Micro assembled LED displays and lighting elements

ABSTRACT

The disclosed technology provides micro-assembled micro-LED displays and lighting elements using arrays of micro-LEDs that are too small (e.g., micro-LEDs with a width or diameter of 10 μm to 50 μm), numerous, or fragile to assemble by conventional means. The disclosed technology provides for micro-LED displays and lighting elements assembled using micro-transfer printing technology. The micro-LEDs can be prepared on a native substrate and printed to a display substrate (e.g., plastic, metal, glass, or other materials), thereby obviating the manufacture of the micro-LEDs on the display substrate. In certain embodiments, the display substrate is transparent and/or flexible.

RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 62/014,077, filed Jun. 18, 2014, titled “MicroAssembled LED Displays and Lighting Elements,” U.S. Provisional PatentApplication No. 62/026,695, filed Jul. 20, 2014, titled “Micro AssembledLED Displays and Lighting Elements,” U.S. Provisional Patent ApplicationNo. 62/029,533, filed Jul. 27, 2014, titled “Micro Assembled LEDDisplays and Lighting Elements,” U.S. Provisional Patent Application No.62/055,485, filed Sep. 25, 2014, titled “Interconnection ArchitecturesAdvantageous for Micro-LED Displays Assembled via Micro TransferPrinting,” U.S. Provisional Patent Application No. 62/056,419, filedSep. 26, 2014, titled “Interconnection Architectures Advantageous forMicro-LED Displays Assembled via Micro Transfer Printing,” U.S.Provisional Patent Application No. 62/131,230, filed Mar. 10, 2015,titled “Passive Matrix Display with Bottom Emitting Inorganic MicroScale Light Emitting Diodes,” U.S. Provisional Patent Application No.62/148,603, filed Apr. 16, 2015 and entitled “Micro Assembled Micro LEDDisplays and Lighting Elements,” and U.S. Provisional Patent ApplicationNo. 62/169,531, filed Jun. 1, 2015 and entitled “Micro Assembled MicroLED Displays and Lighting Elements,” the contents of each of which areincorporated by reference herein in their entireties.

FIELD OF INVENTION

Described herein are micro-assembled inorganic light-emitting diode(i.e., micro-LED) displays and lighting elements featuring arrays ofmicro-LEDs that are too small, numerous, or fragile to be assembled byconventional means.

BACKGROUND

Flat-panel displays are typically constructed with an array of lightemitters distributed over a flat substrate surface. With the exceptionof plasma televisions, emissive flat-panel displays often rely on either(i) a backlight with pixel light control provided by liquid crystals andcolor filters (e.g., liquid crystal displays), (ii) organic coloredlight emitters (e.g., organic light-emitting diode displays), or (iii)organic white-light emitters with color filters (e.g., white organiclight-emitting diode displays). Importantly, all three of theseflat-panel display technologies are area emitters, that is, the entirearea of each pixel is filled with the light emitter or light controller.Most of these displays are active-matrix displays that rely on localcircuits formed on the substrate to control the pixel. These circuits (asingle transistor for liquid crystal displays and two or moretransistors for organic light-emitting diode displays) requiresignificant area on the substrate, reducing the area available for lightemission. Organic light-emitting diode displays typically have a 60%fill factor, also referred to as an active light-emitting area oraperture ratio, and liquid crystal displays can have an even larger fillfactor depending on the display size and resolution.

Inorganic light-emitting diodes (LEDs) are typically manufactured usinga semiconductor process requiring the use of various chemicals andmaterials. These manufacturing methods require the use of a rigidsubstrate, such as a sapphire substrate or a silicon substrate, thatdoes not melt during the high-temperature manufacturing process. Afterfabricating the LEDs on the rigid substrate, the wafers are often cut upto form individual LEDs that are used in displays.

Early LED applications in displays include hand-held calculators withnumeric LED displays. More recently, LEDs have been integrated asbacklights for displays. Integrating LEDs in larger displays, such asdisplay panels, involves complex wiring to each individual LED in thedisplay panel. The use of LEDs in displays, such as RGB LED displays,continues to present numerous challenges, including increasedcomplexity, limited display format, increased manufacturing costs, andreduced manufacturing yields. For example, a display with a resolutionof 1280 by 720 includes 921,600 pixels. For a RGB LED display, eachpixel must typically include three LEDs (a red, a green, and a blue LED)in each pixel. Thus, the display in this example must use 2,764,800LEDs. In some cases, all of these LEDs must be arranged in a displaythat measures a few inches on the diagonal. Not only must these LEDs besmall, but the LEDs must be arranged in an array with the appropriatewiring and driving circuitry. Moreover, the materials used to createeach color of LED vary. Arranging different color LEDs duringmanufacture as required for a RGB display is extremely difficult.Semiconductor chip- or die-automated assembly equipment typically usesvacuum-operated placement heads, such as vacuum grippers orpick-and-place tools, to pick up and apply devices to a substrate. It isdifficult to pick up and place ultra-thin and small devices using thistechnology.

Further, LEDs are typically formed with terminals on different faces ofthe micro-LED. These vertical LEDs are challenged in electricallyisolating the anode and cathode during the process of interconnection.This necessitates depositing a vertical insulator between the terminals,e.g., in the robotic assembly of the LED display. For example, if oneterminal is on the bottom and one terminal is on the top, the terminalsoccupy the same space in the x-y plane and a robust insulator isrequired. The panel-level formation of vertical electrical insulationbetween the two terminals of the LEDs adds additional steps and layersto the display, adding increased complexity in the display application.

For these reasons, among others, it is difficult and expensive toprovide high-resolution RGB LED displays for consumers. Thus, there is aneed for systems and methods of manufacturing displays using LEDs thatprovides low-cost manufacturing, improved yield, and improvedreliability for the systems.

SUMMARY

Described herein are micro-assembled inorganic light-emitting diode(e.g., micro-LED) displays and lighting elements featuring arrays ofmicro-LEDs that are too small, numerous, or fragile to be assembled byconventional means (e.g., micro-LEDs with a width, length, height and/ordiameter of 0.5 μm to 50 μm; e.g., a width of 1-50 μm, a length of 5-500μm and a height of 0.5-50 μm). Rather, these displays are assembledusing micro-transfer printing technology. The micro-LEDs can be preparedon a native substrate using high-temperature manufacturing techniquesand printed to a non-native display substrate (e.g., polymer, plastic,resin, polyimide, polyethylene naphthalate, polyethylene terephthalate,metal, metal foil, glass, and sapphire, transparent materials, orflexible materials separate and distinct from the native substrate onwhich the micro-LED are originally made), thereby obviating themanufacture of the micro-LEDs on the display substrate which, amongother things, cannot withstand the temperatures necessary to constructthe semiconductor elements.

Micro-transfer printed micro-LEDs are bright (e.g., intensities from 300W/cm² to 700 W/cm²) and enable low power consumption. The displays canutilize a transparent (e.g., plastic, sapphire, or glass) substrate, andcan be made lightweight or flexible, or both. Because the micro-LEDstake up a small proportion of the display area, and because themicro-LED wiring can be fine or transparent, the display itself can betransparent or semi-transparent. The displays can emit light from thefront side, the back side, or both sides. In some embodiments, thedisplay has an adhesive layer on one side, producing a decal-likedisplay.

The sparsely distributed micro-LEDs allow for new functions includingmicro-sensors, power harvesting devices, gesture sensors (both contactand non-contact), image capture devices, and the like. The displays canalso include micro-transfer printed micro integrated circuits, whichprovide CMOS performance and in some embodiments, embedded memory (e.g.,non-volatile memory).

The active light-emitting area of an LED pixel is small and takes upminimal pixel area relative to conventional displays in which thesemiconductor material occupies the entire display panel or asubstantial portion thereof. For example, semiconductor material in thedisclosed displays is only needed in locations of active elements, e.g.,in certain embodiments, covering no greater than 40%, 30%, 20%, 10%, 5%,3%, 1%, 0.5%, or 0.1% of the viewing area of the display. Thus, it ispossible to manufacture displays with low fill factors (e.g., no greaterthan 40%, 30%, 20%, 10%, 5%, 3%, 1%, 0.5%, or 0.1%) without compromisingdisplay quality, due in part to the brightness of micro-LEDs, theefficiency of crystalline semiconductor substrates, and the ability toassemble the micro-LEDs in arrays using the manufacturing techniquesdescribed herein.

For example, in some embodiments, driving circuits are located in one ormore pixels (e.g., on the same layer as the micro-LEDs). For example,the drive circuits may use only a small portion of a pixel (e.g., anarea, for example, of 10 to 60 μm by 5 to 50 μm). The circuits requiredto drive micro-LEDS can consume, for example, less than 10%, 5%, 1%,0.5%, or 0.1% of a pixel area, thereby allowing space to be availablefor other uses and/or improved transparency. For example, more complexcircuits or multiple emitters can be placed at each pixel locationwithout a loss in light emission or efficiency. In contrast, if multipleemitters and/or other active elements are included at each pixellocation using other flat-panel display technologies, the area availablefor each pixel will be reduced, thereby resulting in reduced lightoutput or lifetime. Thus, the disclosed micro-LED displays, including,for example, displays utilizing micro-LEDs on a display substrate, allowfor more complexity, additional light emitters, or additionalfunctionality to be placed in each pixel without significantly impacting(e.g., without any impact) display quality.

In certain embodiments, a yield of 99.99% or greater is achieved bymicro-transfer printing micro-LEDs to a display substrate. Locatingmultiple inorganic micro-LEDs at each pixel site enables severalpossible technical advantages. Further, the display yield can beincreased by locating redundant inorganic micro-LEDs at each lightemitter or pixel site. For example, display yield is improved, in someembodiments, by using two or more identical light emitters at each pixelsite because, for example, the display appears to function properly evenif one light emitter at each pixel site, for example, is faulty.Redundant micro-LEDs, in certain embodiments, are electrically connectedto the display upon a determination (e.g., during manufacturing or priorto distribution of the display) that a primary micro-LED ismalfunctioning.

Further, additional emitters of different colors, in some embodiments,are provided within a pixel at no significant cost in substrate area orpixel performance. Additional colors can broaden the color gamut, forexample, by adding yellow or cyan to the conventional red, green, andblue emitters. In some embodiments, 3D displays are provided using thedisclosed technology. For example, a display, in some embodiments,utilizes two slightly different red, green, and blue emitters, therebyproviding a 3-D display without decreasing the display frame rate. Morecomplex control schemes are possible, such as, for example,update-on-demand. Furthermore, in some embodiments, local light sensorscan be used to locally (or globally) calibrate the micro-LEDs (e.g., inreal time). In certain embodiments, other micro devices, in addition tomicro-LEDs, can be placed within each pixel. For example, micro sensingand micro integrated circuits (e.g., micro display drivers) can beplaced within a pixel. An antenna, in some embodiments, is locatedwithin each pixel. The antenna can be used to stream power or data intothe display using wireless signals/communications.

In certain embodiments, the disclosed technology includes advantageousinterconnection architectures for micro-LED displays, for example,displays assembled via micro-transfer printing.

Typically, LEDs are formed with terminals on different faces of themicro-LED. Vertical LEDs are challenged in electrically isolating theanode and cathode during the process of interconnection. Thisnecessitates depositing a vertical insulator between the terminals,e.g., in the robotic assembly of the LED display. For example, if oneterminal is on the bottom and one terminal is on the top, the terminalsoccupy the same space in the x-y plane, and a robust insulator isrequired.

Additionally, horizontal separation of the contact pads allows theconnections to the terminals of each micro-LED to be formed on a singlelevel, thereby reducing the number of levels in the display andimproving placement accuracy. In certain embodiments, micro-LEDs areassembled (e.g., via micro-transfer printing) onto the insulator andholes are created in the insulator to access column lines below theinsulator. Thus, this architecture reduces the number of levels requiredto form the display.

Moreover, horizontal separation of contact pads on a micro-LED offersbenefits not available from vertical LED structures. For example,displays that use vertical LED structures require the panel-levelformation of vertical electrical insulation between the two terminals(contact pads) of the LEDs. By contrast, the disclosed technology avoidsthis problem, in certain embodiments, by placing the terminals on thesame face of the micro-LED. Horizontal separation of the LED contactpads facilitates electrical isolation by dint of the horizontalseparation of conductors, thereby avoiding a vertical electricalinsulation requirement.

The disclosed technology, in certain embodiments, provides for anelongated micro-LED (e.g., a rectangular LED with a large aspect ratio)with horizontally separated contact pads. This configuration reduces theplacement accuracy of display panel conductors required to assemble themicro-LEDs to the display panel. Moreover, fine lithography in the LEDconstruction process can be used to minimize the separation distancebetween the terminals and other elements in the LED structure (e.g., aseparation distance of distance of 100 nm to 200 microns), thusincreasing the potential size of the micro-LED terminals. Reducing thelateral separation between the terminals and the LED structure elements,increasing the size of the terminals (within the confines of thedimensions of the LED), and horizontally separating the terminalsincreases the manufacturing tolerance for registration and lithographyerrors between the assembled micro-LEDs and the relatively coarseconductive lines used to interconnect the assembled micro-LEDs on thedisplay substrate.

Furthermore, stacked transparent (or semi-transparent) displays aredescribed herein, which allow for tunable brightness, defectcompensation, increased definition, and/or 2.5-D or 3-D viewing.

Also described herein are displays formed of multiple integrateddisplays occupying the same viewing area as independent driver chips,displays with supplementary RGB inorganic micro-LEDs, multi-modedisplays with a reflective display element and micro-LED emitter in thesame pixel, displays having pixels with yellow micro-LEDs (and/or othernon-traditional RGB colors, such as cyan) for more visually perfectdevices, and micro-assembled micro-LED displays with, for example, up to9 micro-LEDs per pixel. The disclosed technology also facilitatesphotoluminescent or functional testing of micro-assembled micro-LEDs.

The disclosed technology, in certain embodiments, utilizesmicro-transfer printing techniques to form imaging devices such asmicro-LED display devices. For example, in certain embodiments,electronically active components are transferred from a native substrate(e.g., inorganic semiconductor materials, single crystalline siliconwafers, silicon on insulator wafers, polycrystalline silicon wafers andGaAs wafers, Si (1 1 1), GaN, Sapphire, InP, InAlP, InGaAs, AlGaAs,GaSb, GaAlSb, AlSb, InSb, InGaAlSbAs, InAlSb, and InGaP) to a displaysubstrate (e.g., a non-native substrate such as glass, plastic, or metalused to, for example, form an array of the active components on thenon-native substrate). The transfer is, in some embodiments, performedusing an elastomer stamp and/or electrostatic stamp. The release of theactive components is controlled and predictable, thereby enablingproduction of the micro-LED displays described herein usingmicro-transfer printing techniques.

For example, micro-structured stamps, such as an elastomer stamp orelectrostatic stamp (or other transfer device), can be used to pick upmicro devices (e.g., micro-LEDs, sensors, or integrated circuits),transport the micro devices to a destination display substrate, andprint the micro devices onto the display substrate. Surface adhesionforces can be used to control the selection and printing of thesedevices onto the display substrate. This process can be performed inmassively in parallel, transferring hundreds to thousands of discretestructures in a single pick-up-and-print operation.

In one aspect, the invention is directed to an inorganic light-emittingdiode display, the display comprising: a plurality of inorganiclight-emitting diodes assembled in an array on a display substratenon-native to the plurality of light-emitting diodes, wherein eachlight-emitting diode of the array comprises a first metal terminal on afirst side of the corresponding light-emitting diode horizontallyseparated from a second metal terminal on the first side of the samelight-emitting diode by a horizontal distance, wherein the horizontaldistance is from 100 nm to 20 microns.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm. In certain embodiments, each of theplurality of light emitters has a width from 2 to 5 μm, 5 to 10 μm, 10to 20 μm, or 20 to 50 μm. In certain embodiments, each of the pluralityof light emitters has a length from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm,or 20 to 50 μm. In certain embodiments, each of the plurality of lightemitters has with a height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or20 to 50 μm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, each light-emitting diode comprises: aconduction layer; and an inorganic light-emitting layer disposed on aportion of the conduction layer, the conduction layer comprising acantilever extension extending beyond an edge of the inorganiclight-emitting layer, wherein the first metal terminal is disposed on aportion of the inorganic light-emitting layer and the second metalterminal is disposed on the cantilever extension of the conductionlayer, wherein a current supplied between the first metal terminal andthe second metal terminal causes the inorganic light-emitting layer toemit light.

In certain embodiments, the lateral conduction layer comprises at leastone member selected from the group consisting of a metal mirror,dielectric mirror, high refractive index semiconductor, andsemiconductor substantially transparent to the light emitted from thelight-emitting diode, thereby forming an upward emitting display.

In certain embodiments, the lateral conduction layer comprises at leastone member selected from the group consisting of a semiconductorsubstantially transparent to the light emitted from the LED, transparentconductive oxide, and thin metal mesh.

In certain embodiments, the first and second metal terminals aretransparent. In certain embodiments, the first and second metalterminals comprise at least one member selected from the groupconsisting of: ITO, ZnO, carbon nanotube films, aluminum, silver, gold,nickel, platinum, titanium, and fine metal meshes.

In certain embodiments, the display is a downward emitting micro-LEDdisplay such that a majority of light emitted by the plurality oflight-emitting diodes is emitted through the display substrate.

In certain embodiments, the display comprises a plurality of opticalreflection structures, each optical reflection structure located on asame side of a corresponding light-emitting diode of the plurality oflight-emitting diodes as the first metal terminal.

In certain embodiments, the first and second metal terminals are atleast partially reflective, thereby allowing light emitted from arespective light-emitting diode to at least partially reflect off thefirst and second metal terminals and through a second face of eachlight-emitting diode, opposite the first face.

In certain embodiments, the materials located directly below at least aportion of each light-emitting diode are at least partially transparent.

In certain embodiments, the display is an upward emitting micro-LEDdisplay such that a majority of light emitted by the plurality oflight-emitting diodes is emitted in a direction away from the displaysubstrate.

In certain embodiments, the display comprises a plurality of opticalreflection structures, each optical reflection structure locatedunderneath a corresponding light-emitting diode of the plurality oflight-emitting diodes on an opposite side of said light-emitting diodefrom the first metal terminal.

In certain embodiments, the first and second metal terminals are atleast partially transparent, thereby allowing light emitted from arespective light-emitting diode to at least partially pass through thefirst and second metal terminals.

In certain embodiments, the display comprises a plurality of firstinterconnections each electrically connected to the first metal terminalof a corresponding light-emitting diode; and a plurality of secondinterconnections each electrically connected to the second metalterminal of a corresponding light-emitting diode, wherein the pluralityof first interconnections and the plurality of second interconnectionsare on the first face.

In certain embodiments, the plurality of first interconnection featuresand the plurality of second interconnection features are in a singlelithography level.

In certain embodiments, each of the plurality of first interconnectionsis electrically coupled to one column electrode of a plurality of columnelectrodes through a via of a plurality of vias in the insulator, eachvia associated with a light-emitting diode of the plurality oflight-emitting diodes.

In certain embodiments, the plurality of column electrodes, theplurality of first interconnections, and the plurality of secondinterconnections are formed by lithography with a coarser resolutionthan the lithography used to form the first and second metal terminals.

In certain embodiments, each of the light-emitting diodes has a lengthgreater or equal to two times its width. In certain embodiments, foreach light-emitting diode of the plurality of light-emitting diodes, thecorresponding first and second metal terminals cover at least half,two-thirds, or three-quarters of the lateral footprint of thecorresponding light-emitting diode. In certain embodiments, theplurality of light-emitting diodes are assembled via micro-transferprinting.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light. In certainembodiments, the display substrate has a contiguous display substratearea that includes the plurality of light-emitting diodes, eachlight-emitting diode of the plurality of light-emitting diodes has alight-emissive area, and the combined light-emissive areas of theplurality of light-emitting diodes is less than or equal to one-quarterof the contiguous display substrate area.

In certain embodiments, the combined light-emissive areas of theplurality of light-emitting diodes is less than or equal to one eighth,one tenth, one twentieth, one fiftieth, one hundredth, onefive-hundredth, one thousandth, one two-thousandth, or oneten-thousandth of the contiguous display substrate area.

In certain embodiments, for each inorganic light-emitting diode of theplurality of inorganic light-emitting diodes, the horizontal distance isof from 500 nm to 1 μm, 1 μm to 5 μm, 5 μm to 10 μm, or 10 μm to 20 μm.In certain embodiments, for each inorganic light-emitting diode of theplurality of inorganic light-emitting diodes, a surface of the firstmetal terminal and a surface of a second metal terminal share a plane.

In certain embodiments, the display comprises: a plurality of microintegrated circuits on the display substrate, each electricallyconnected with a set of the plurality of light-emitting diodes.

In certain embodiments, each integrated circuit is used to control LEDsthat emit a certain color of light.

In certain embodiments, each set of the plurality of light-emittingdiodes driven by a respective integrated circuit forms an independentsub-display.

In certain embodiments, the display comprises: a plurality of secondinorganic light-emitting diodes assembled in a second array on a seconddisplay substrate non-native to the plurality of second light-emittingdiodes, wherein each second light-emitting diode of the plurality ofsecond light-emitting diodes comprises a first metal terminal on a firstside of the corresponding light-emitting diode horizontally separatedfrom a second metal terminal on the first side of the samelight-emitting diode by a horizontal distance, wherein the horizontaldistance is from 100 nm to 20 microns, wherein the first displaysubstrate and the second substrate are stacked.

In certain embodiments, the display comprises: a plurality of secondinorganic light-emitting diodes assembled in a second array on a side ofthe display substrate opposite the plurality of inorganic light-emittingdiodes, wherein each second light-emitting diode of the plurality ofsecond light-emitting diode comprises a first metal terminal on a firstside of the corresponding light-emitting diode horizontally separatedfrom a second metal terminal on the first side of the samelight-emitting diode by a horizontal distance, wherein the horizontaldistance is from 100 nm to 20 microns, wherein the first displaysubstrate and the second substrate are stacked.

In certain embodiments, the array of the plurality of inorganiclight-emitting diodes has a different resolution than the second arrayof the plurality of second inorganic light-emitting diodes.

In certain embodiments, each of the plurality of inorganiclight-emitting diodes has a first size, each of the plurality of secondinorganic light-emitting diodes has a second size, and the first size isdifferent than the second size.

In another aspect, the invention is directed to a method of forming alight-emitting diode display, the method comprising: forming a pluralityof column lines on a substrate; depositing an insulator on the columnlines; micro-transfer printing a plurality of light-emitting diodes ontothe insulator, wherein each micro light-emitting diode comprises a firstand second metal terminal on a first face of the light-emitting diode,where the substrate is non-native to the plurality of light-emittingdiodes; forming a plurality of holes in the insulator, thereby exposingportions of each of the plurality of column lines; and depositing aplurality of conductive interconnections on the first face, theplurality of conductive interconnections comprising a plurality of rowelectrodes and a plurality of column interconnections, wherein each ofthe plurality of column interconnections electrically connect a columnline to the first metal terminal of a corresponding light-emittingdiode.

In certain embodiments, for each light-emitting diode of the pluralityof light-emitting diodes, the first metal terminal is horizontallyseparated by a horizontal distance from 100 nm to 5 microns from thesecond metal terminal on the first face of the same light-emittingdiode.

In certain embodiments, the first and second metal terminals aretransparent. In certain embodiments, the first and second metalterminals are at least partially transparent, thereby allowing lightemitted from a respective light-emitting diode to at least partiallypass through the first and second metal terminals.

In certain embodiments, the display is a downward emitting micro-LEDdisplay such that a majority of light emitted by the plurality oflight-emitting diodes is emitted through the display substrate.

In certain embodiments, the method comprises depositing a plurality ofoptical reflection structures, each optical reflection structure locatedabove a light-emitting diode of the plurality of light-emitting diodeson an opposite side of said light-emitting diode from the displaysubstrate.

In certain embodiments, the materials located directly below at least aportion of each light-emitting diode are at least partially transparent.

In certain embodiments, the first and second metal terminals are atleast partially reflective, thereby allowing light emitted from arespective light-emitting diode to at least partially reflect off thefirst and second metal terminals and through a second face of eachlight-emitting diode, opposite the first face. In certain embodiments,the first and second metal terminals comprise at least one memberselected from the group consisting of: ITO, ZnO, carbon nanotube films,aluminum, silver, gold, nickel, platinum, titanium, and fine metalmeshes.

In certain embodiments, the display is an upward emitting micro-LEDdisplay such that a majority of light emitted by the plurality oflight-emitting diodes is emitted in a direction away from the displaysubstrate.

In certain embodiments, the method comprises: prior to micro-transferprinting the plurality of light-emitting diodes, depositing a pluralityof optical reflection structures, each optical reflection structurelocated underneath a corresponding light-emitting diode of the pluralityof light-emitting diodes.

In certain embodiments, each light-emitting diode comprises: aconduction layer; and an inorganic light-emitting layer disposed on aportion of the conduction layer, the conduction layer comprising acantilever extension extending beyond an edge of the inorganiclight-emitting layer, wherein the first metal terminal is disposed on aportion of the inorganic light-emitting layer and the second metalterminal is disposed on the cantilever extension of the conductionlayer, wherein a current supplied between the first metal terminal andthe second metal terminal causes the inorganic light-emitting layer toemit light.

In certain embodiments, the lateral conduction layer comprises at leastone member selected from the group consisting of a metal mirror,dielectric mirror, high refractive index semiconductor, andsemiconductor substantially transparent to the light emitted from thelight-emitting diode, thereby forming an upward emitting display.

In certain embodiments, the lateral conduction layer comprises at leastone member selected from the group consisting of a semiconductorsubstantially transparent to the light emitted from the LED, transparentconductive oxide, and thin metal mesh.

In certain embodiments, micro-transfer printing the plurality oflight-emitting diodes comprises: providing a transfer device with aportion of the plurality of light-emitting diodes removably attachedthereto, wherein said transfer device comprises a three-dimensionalfeature in at least partial contact with the portion of the plurality oflight-emitting diodes; contacting the portion of the plurality oflight-emitting diodes removably attached to said transfer device withthe receiving surface of the substrate; and following said contacting ofthe portion of the plurality of light-emitting diodes with saidreceiving surface, separating said transfer device from the portion ofthe plurality of light-emitting diodes, wherein the portion of theplurality of light-emitting diodes is transferred onto said receivingsurface.

In certain embodiments, the method comprises: a plurality of columnelectrodes, each electrically connected to a respective one of theplurality of first interconnections; and an insulator between theplurality of column electrodes and the plurality of light-emittingdiodes, wherein the plurality of second interconnections comprise aplurality of row electrodes electrically connected to the second metalterminal of at least one of the plurality of light-emitting diodes.

In certain embodiments, each of the plurality of first interconnectionsis electrically coupled to one of the column electrodes of the pluralityof column electrodes through a via of a plurality of vias in theinsulator.

In certain embodiments, the plurality of column electrodes, theplurality of first interconnections, and the plurality of secondinterconnections are formed by lithography with a coarser resolutionthan the lithography used to form the first and second metal terminals.

In certain embodiments, the plurality of column electrodes, theplurality of first interconnections, and the plurality of secondinterconnections have a minimum line and space dimensional range of 2microns to 2 millimeters.

In certain embodiments, each of the light-emitting diodes has a lengthgreater or equal to two times its width.

In certain embodiments, the plurality of first interconnection featuresand the plurality of second interconnection features are in a singlelithography level.

In certain embodiments, for each light-emitting diode of the pluralityof light-emitting diodes, the corresponding first and second metalterminals cover at least half, two-thirds, or three-quarters the lateralfootprint of the corresponding light-emitting diode.

In certain embodiments, the first face of each of the plurality oflight-emitting diodes is on a side of each diode away from the displaysubstrate.

In certain embodiments, the non-native substrate is a member selectedfrom the group consisting of polymer, plastic, resin, polyimide, PEN,PET, metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, each of the plurality of light-emitting diodeshas a width from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each of the plurality of light-emitting diodes hasa length from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each of the plurality of light-emitting diodes haswith a height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes plurality of light-emitting diodes, eachlight-emitting diode of the plurality of light-emitting diodes has alight-emissive area, and the combined light-emissive areas of theplurality of light-emitting diodes is less than or equal to one-quarterof the contiguous display substrate area.

In certain embodiments, the combined light-emissive areas of the lightemitters is less than or equal to one eighth, one tenth, one twentieth,one fiftieth, one hundredth, one five-hundredth, one thousandth, onetwo-thousandth, or one ten-thousandth of the contiguous displaysubstrate area.

In certain embodiments, the plurality of conductive interconnections aredeposited in a single step.

In certain embodiments, the method comprises: micro-transfer printing aplurality of micro integrated circuits on the display substrate, eachelectrically connected with a set of the plurality of light-emittingdiodes. In certain embodiments, each integrated circuit is used tocontrol LEDs that emit a certain color of light.

In certain embodiments, the method comprises: micro-transfer printing aplurality of second inorganic light-emitting diodes in a second array ona second display substrate non-native to the plurality of secondlight-emitting diodes, wherein each second light-emitting diode of theplurality of second light-emitting diodes comprises a first metalterminal on a first side of the corresponding light-emitting diodehorizontally separated from a second metal terminal on the first side ofthe same light-emitting diode by a horizontal distance, wherein thehorizontal distance is from 100 nm to 20 microns, wherein the firstdisplay substrate and the second substrate are stacked.

In certain embodiments, the method comprises: micro-transfer printing aplurality of second inorganic light-emitting diodes in a second array ona side of the display substrate opposite the plurality of inorganiclight-emitting diodes, wherein each second light-emitting diode of theplurality of second light-emitting diode comprises a first metalterminal on a first side of the corresponding light-emitting diodehorizontally separated from a second metal terminal on the first side ofthe same light-emitting diode by a horizontal distance, wherein thehorizontal distance is from 100 nm to 20 microns, wherein the firstdisplay substrate and the second substrate are stacked.

In certain embodiments, the array of the plurality of inorganiclight-emitting diodes has a different resolution than the second arrayof the plurality of second inorganic light-emitting diodes.

In certain embodiments, each of the plurality of inorganiclight-emitting diodes has a first size, each of the plurality of secondinorganic light-emitting diodes has a second size, and the first size isdifferent than the second size.

In another aspect, the invention is directed to a display comprising: adisplay substrate; a first patterned metal layer on a surface of thedisplay substrate; a dielectric layer on the display substrate and thefirst patterned metal layer; a polymer layer on the dielectric layer; aplurality of light emitters on a surface of the polymer layer, eachlight emitter of the plurality of light emitters having an anode and acathode on a same side of the respective light emitter, wherein thedisplay substrate is non-native to the plurality of light emitters; aplurality of vias formed through the polymer and dielectric layer, eachvia associated with a corresponding light emitter of the plurality oflight emitters; and a second patterned metal layer, the second patternedmetal layer comprising a plurality of anode interconnections and aplurality of cathode interconnections in a single layer, each anodeinterconnection electrically connecting the anode of a correspondinglight emitter of the plurality of light emitters to the first patternedmetal layer through a corresponding via of the plurality of vias andeach cathode interconnections electrically contracting the cathode of acorresponding light emitter of the plurality of light emitters.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separated by a horizontal distance, wherein thehorizontal distance is from 100 nm to 500 nm, 500 nm to 1 micron, 1micron to 20 microns, 20 microns to 50 microns, or 50 microns to 100microns.

In certain embodiments, the plurality of light emitters comprise aplurality of inorganic light emitting diodes.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm.

In certain embodiments, each of the plurality of light emitters has awidth from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each of the plurality of light emitters has alength from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each of the plurality of light emitters has with aheight from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area, the plurality of light emitters each have alight-emissive area, and the combined light-emissive areas of theplurality of light emitters is less than or equal to one-quarter of thecontiguous display substrate area.

In certain embodiments, the combined light-emissive areas of theplurality of light emitters is less than or equal to one eighth, onetenth, one twentieth, one fiftieth, one hundredth, one five-hundredth,one thousandth, one two-thousandth, or one ten-thousandth of thecontiguous display substrate area.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the first patterned metal layer comprises ametal stack. In certain embodiments, the metal stack comprises Aluminumand Titanium. In certain embodiments, the Titanium is on the Aluminum.

In certain embodiments, the polymer layer is a photosensitivenegative-acting semiconductor-grade epoxy.

In certain embodiments, the plurality of light emitters having beenmicro-transfer printed on the surface of the polymer layer using a printtool.

In certain embodiments, the print tool is a viscoelastic elastomerstamp.

In certain embodiments, the second patterned metal layer comprises ametal stack. In certain embodiments, the metal stack comprises Ti/Al/Ti.

In certain embodiments, the second patterned metal layer comprises aplurality of pads on the display substrate.

In certain embodiments, the plurality of light emitters comprises aplurality of red light emitters that emit red light, a plurality ofgreen light emitters that emit green light, and a plurality of bluelight emitters that emit blue light.

In certain embodiments, at least one of the anode and cathode of eachlight emitter of the plurality of light emitters is formed on alight-emitter dielectric layer.

In certain embodiments, the dielectric layer is silicon nitride.

In certain embodiments, the display substrate is flexible.

In another aspect the invention is directed to a method of forming adisplay, the method comprising: depositing a first metal layer on adisplay substrate; patterning the first metal layer to form a firstpatterned metal layer; depositing a layer of dielectric onto the firstpatterned metal layer to create an electrically insulating layer;applying an uncured polymer layer; micro-transfer printing a pluralityof light emitters from a native substrate onto the polymer, wherein thenative substrate is native to at least a portion of the plurality oflight emitters and the light emitters each have an anode and a cathodefor providing power to the light emitters; exposing the polymer toultraviolet light to cure the polymer; forming a plurality of viasthrough the cured polymer and dielectric layer to expose a portion ofthe first patterned metal layer; depositing a second metal layer,wherein the second metal layer contacts an anode and a cathode of eachlight emitter of the plurality of light emitters; and patterning thesecond metal layer to form the second patterned metal layer, wherein thesecond patterned metal layer comprises a plurality of anodeinterconnections and a plurality of cathode interconnections, each anodeinterconnection electrically connecting the anode of a correspondinglight emitter of the plurality of light emitters to the first patternedmetal layer through a corresponding via of the plurality of vias andeach cathode interconnection electrically contacting the cathode of acorresponding light emitter of the plurality of light emitters.

In certain embodiments, the plurality of light emitters comprises aplurality of inorganic light emitting diodes.

In certain embodiments, the method comprises: cutting the displaysubstrate into a plurality of displays.

In certain embodiments, the method comprises: prior to cutting thenon-native wafer into the plurality of displays, coating the wafer witha protective photoresist layer; and after cutting the display substrateinto the plurality of displays, removing the protective photoresistlayer from each display of the plurality of displays after cutting thedisplay substrate into the plurality of displays.

In certain embodiments, the method comprises: providing a passive-matrixdriver integrated circuit on receiving pads on a surface of thenon-native wafer.

In certain embodiments, the method comprises: burning-in each lightemitter of the plurality of light emitters.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separate by a horizontal distance, wherein thehorizontal distance is 100 nm to 100 microns.

In certain embodiments, the polymer is a photosensitive negative-actingsemiconductor-grade epoxy.

In certain embodiments, the first metal layer is deposited using metalphysical vapor deposition. In certain embodiments, the first metal layeris patterned using photolithography.

In certain embodiments, patterning the first metal layer comprises:prior to depositing the first metal layer, applying a negative-actingphotoresist to the first metal layer, selectively exposing thephotoresist to light (e.g., using a mask), and developing thephotoresist to form a lift-off template; and after depositing the firstmetal layer, removing the lift-off template, thereby forming the firstpatterned metal layer.

In certain embodiments, the first metal layer comprises a metal stack ofTitanium on Aluminum on Titanium.

In certain embodiments, depositing the first metal layer comprisingdepositing the first metal layer using e-beam evaporation.

In certain embodiments, patterning the second metal layer comprises:patterning a lift-off mask in a negative acting photoresist; depositinga metal stack; and lifting-off of the photoresist mask to leave behindthe second patterned metal layer.

In certain embodiments, the second metal layer comprises a metal stack.

In certain embodiments, the metal stack comprises Ti/Al/Ti.

In certain embodiments, the method comprises removing one or moresolvents from the polymer using one or more heat treatments.

In certain embodiments, micro-transfer printing the plurality of lightemitters comprises micro-transfer printing the plurality of lightemitters using a print tool.

In certain embodiments, the print tool comprises a viscoelasticelastomer stamp.

In certain embodiments, micro-transfer printing the plurality of lightemitters comprises using kinetically tunable adhesion between theplurality of light emitters and the viscoelastic elastomer surface.

In certain embodiments, micro-transfer printing the plurality of lightemitters comprises: picking up at least a portion of the plurality oflight emitters from the native substrate by contacting a viscoelasticelastomer stamp to a first surface of each of the light emitters in theportion of the plurality of light emitters and moving the viscoelasticelastomer stamp away from the native substrate at a first rate leadingto an effective increase in the adhesion between the elastomer and theportion of the plurality of light emitters; and printing the portion ofthe plurality of light emitters to the non-native substrate bycontacting a second surface of each of the light emitters picked up bythe viscoelastic elastomer stamp to the polymer and moving theviscoelastic elastomer stamp away from the display substrate at a secondrate, thereby leaving the light emitters picked up by the viscoelasticelastomer stamp on the polymer, wherein the second rate is less than thefirst rate.

In certain embodiments, the method comprises laterally shearing thestamp during the micro transfer printing process.

In certain embodiments, the plurality of light emitters comprises aplurality of red light emitters that emit red light, a plurality ofgreen light emitters that emit green light, and a plurality of bluelight emitters that emit blue light.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, micro-transfer printing the plurality of lightemitters from a native substrate onto the polymer comprises performingat least two micro transfer printing operations.

In certain embodiments, micro-transfer printing the plurality of lightemitters from a native substrate onto the polymer comprises:micro-transfer printing a plurality of red light emitters that emit redlight from a red light emitter native substrate; micro-transfer printinga plurality of green light emitters that emit green light from a greenlight emitter native substrate; and micro-transfer printing a pluralityof blue light emitters that emit blue light from a blue light emitternative substrate, wherein the plurality of light emitters comprises theplurality of red light emitters, the plurality of green light emitters,and the plurality of blue light emitters.

In certain embodiments, the display substrate is flexible.

In another aspect, the invention is directed to an inorganiclight-emitting diode comprising: a conduction layer; an inorganiclight-emitting layer disposed on a portion of the conduction layer, theconduction layer comprising a cantilever extension extending beyond anedge of the inorganic light-emitting layer; a first metal terminaldisposed on a portion of the inorganic light-emitting layer; a secondmetal terminal disposed on the cantilever extension of the conductionlayer, wherein a current supplied between the first metal terminal andthe second metal terminal causes the inorganic light-emitting layer toemit light; and a dielectric layer disposed on at least a portion of theinorganic light-emitting layer, wherein the dielectric layerelectrically isolates the first metal terminal from the second metalterminal, wherein the first and second metal terminals are on a sameside of the inorganic light-emitting diode and are separated by ahorizontal distance of from 100 nm to 20 μm.

In certain embodiments, the inorganic light-emitting diode has a widthfrom 0.5 to 2 μm, 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, the inorganic light-emitting diode has a lengthfrom 0.5 to 2 μm, 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, the inorganic light-emitting diode has with aheight from 0.5 to 2 μm, 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50μm. In certain embodiments, the horizontal distance is of from 500 nm to1 μm, 1 μm to 5 μm, 5 μm to 10 μm, or 10 μm to 20 μm.

In certain embodiments, a surface of the first metal terminal and asurface of a second metal terminal share a plane.

In certain embodiments, for each light emitting diode of the pluralityof light emitting diodes, the corresponding first and second metalterminals cover at least half, two-thirds, or three-quarters of thelateral footprint of the corresponding light emitting diode.

In certain embodiments, the lateral conduction layer comprises at leastone member selected from the group consisting of a metal mirror,dielectric mirror, high refractive index semiconductor, andsemiconductor substantially transparent to the light emitted from thelight emitting diode, thereby forming an upward emitting display. Incertain embodiments, the lateral conduction layer comprises at least onemember selected from the group consisting of a semiconductorsubstantially transparent to the light emitted from the LED, transparentconductive oxide, and thin metal mesh.

In certain embodiments, the first and second metal terminals aretransparent. In certain embodiments, the first and second metalterminals comprise at least one member selected from the groupconsisting of: ITO, ZnO, carbon nanotube films, aluminum, silver, gold,nickel, platinum, titanium, and fine metal meshes.

In another aspect, the invention is directed to an inorganiclight-emitting diode display comprising a plurality of the inorganiclight-emitting diodes, wherein the plurality of inorganic light-emittingdiodes are disposed on a substrate.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, the method further comprises a plurality ofoptical reflection structures, each optical reflection structure locatedon a same side of a corresponding light emitting diode of the pluralityof light emitting diodes as the first metal terminal.

In certain embodiments, the method further comprises a plurality ofoptical reflection structures, each optical reflection structure locatedunderneath a corresponding light emitting diode of the plurality oflight emitting diodes on an opposite side of said light emitting diodefrom the first metal terminal.

In certain embodiments, the method further comprises: a plurality offirst interconnections each electrically connected to the first metalterminal of a corresponding light emitting diode; and a plurality ofsecond interconnections each electrically connected to the second metalterminal of a corresponding light emitting diode, wherein the pluralityof first interconnections and the plurality of second interconnectionsare on the first face.

In certain embodiments, the plurality of first interconnection featuresand the plurality of second interconnection features are in a singlelithography level.

In certain embodiments, each of the plurality of first interconnectionsis electrically coupled to one column electrode of a plurality of columnelectrodes through a via of a plurality of vias in the insulator, eachvia associated with a light emitting diode of the plurality of lightemitting diodes.

In certain embodiments, the plurality of column electrodes, theplurality of first interconnections, and the plurality of secondinterconnections are formed by lithography with a coarser resolutionthan the lithography used to form the first and second metal terminals.

In certain embodiments, each of the light emitting diodes has a lengthgreater or equal to two times its width.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes the plurality of light emitting diodes,each light emitting diode of the plurality of light emitting diodes hasa light-emissive area, and the combined light-emissive areas of theplurality of light emitting diodes is less than or equal to one-quarterof the contiguous display substrate area.

In certain embodiments, the combined light-emissive areas of theplurality of light emitting diodes is less than or equal to one eighth,one tenth, one twentieth, one fiftieth, one hundredth, onefive-hundredth, one thousandth, one two-thousandth, or oneten-thousandth of the contiguous display substrate area.

In another aspect, the invention is directed to an inorganic lightemitting diode (LED) display, the display comprising: a displaysubstrate; a plurality of pixels, each pixel comprising a set of primaryinorganic LEDs connected to a display circuit and a set of redundantinorganic LEDs unconnected to the display circuit, wherein each of theredundant inorganic LEDs can be electrically connected to the displaycircuit to replace a corresponding defective LED that is one of theprimary inorganic LEDs, wherein: each primary and redundant inorganicLED is formed in or on a native substrate distinct and separate from thedisplay substrate; and the native substrates are on the displaysubstrate.

In certain embodiments, the display comprises a redundant LEDelectrically connected to the display circuit.

In certain embodiments, the display comprises a conductive jumperelectrically connecting a redundant LED to the display circuit.

In another aspect, the invention is directed to an inorganic lightemitting diode (LED) display, the display comprising: a displaysubstrate; a plurality of pixels, each pixel comprising a set of primaryinorganic LEDs and a set of redundant inorganic LEDs, wherein: eachprimary and redundant inorganic LED is formed in or on a nativesubstrate distinct and separate from the display substrate; the nativesubstrates are on the display substrate; and each inorganic LED of theredundant set is connected in series with a resistor to form aLED-resistor pair, and each LED-resistor pair is wired in parallel witha inorganic LED of the primary set.

In another aspect, the invention is directed to an inorganic lightemitting diode (LED) display, the display comprising: a displaysubstrate; a plurality of pixels, each pixel comprising a set of primaryinorganic LEDs and a set of redundant inorganic LEDs, wherein: eachprimary and redundant inorganic LED is formed in or on a nativesubstrate distinct and separate from the display substrate; the nativesubstrates are on the display substrate; and each inorganic LED of theredundant set is connected in series with a diode to form an LED-diodepair, and each LED-diode pair is wired in parallel with an inorganic LEDof the primary set.

In certain embodiments, the set of primary inorganic LEDs comprises aplurality of red inorganic LED that emits red light, a plurality ofgreen inorganic LED that emits green light, and a plurality of blueinorganic LED that emits blue light, and the set of redundant inorganicLEDs comprises a plurality of redundant red inorganic LED that emits redlight, a plurality of redundant green inorganic LED that emits greenlight, and a plurality of redundant blue inorganic LED that emits bluelight.

In certain embodiments, the set of primary inorganic LEDs comprises aplurality of yellow inorganic LEDs that emit yellow light; and the setof redundant inorganic LEDs comprises a plurality of redundant yellowinorganic LEDs that emit yellow light.

In certain embodiments, the set of primary inorganic LEDs and the set ofredundant inorganic LEDs are directly on the display substrate.

In certain embodiments, each pixel comprises an inorganic integratedcircuit electrically connected to each inorganic LED in a respectivepixel.

In certain embodiments, each pixel comprises a primary micro integratedcircuit and a redundant micro integrated circuit.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, each inorganic LED has a width from 2 to 5 μm, 5to 10 μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, eachinorganic LED has a length from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or20 to 50 μm. In certain embodiments, each inorganic LED has with aheight from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes the set of primary inorganic LEDs and theset of redundant inorganic LEDs, each LED has a light-emissive area, andthe combined light-emissive areas of LEDs is less than or equal toone-quarter of the contiguous display substrate area.

In certain embodiments, the combined light-emissive areas of the LEDs isless than or equal to one eighth, one tenth, one twentieth, onefiftieth, one hundredth, one five-hundredth, one thousandth, onetwo-thousandth, or one ten-thousandth of the contiguous displaysubstrate area.

In another aspect, the invention is direct to a method of inorganicassembling a inorganic light emitting diode (LED) display, the methodcomprising: forming a plurality of printable inorganic LEDs in or on oneor more native substrates; transfer printing the plurality of printableinorganic LEDs onto a display substrate separate and distinct from theone or more native substrates to form a plurality of pixels, whereineach pixel comprises a set of primary inorganic LEDs and a set ofredundant inorganic LEDs; connecting the primary inorganic LEDs to adisplay circuit; and testing the display to identify defective primaryinorganic LEDs.

In certain embodiments, the set of primary inorganic LEDs comprises aplurality of red inorganic LEDs that emit red light, a plurality ofgreen inorganic LEDs that emit green light, and a plurality of blueinorganic LEDs that emit blue light, and the set of redundant inorganicLEDs comprises a plurality of redundant red inorganic LEDs that emit redlight, a plurality of redundant green inorganic LEDs that emit greenlight, and a plurality of redundant blue inorganic LEDs that emit bluelight.

In certain embodiments, the set of primary inorganic LEDs comprises aplurality of yellow inorganic LEDs that emit yellow light; and the setof redundant inorganic LEDs comprises a plurality of redundant yellowinorganic LEDs that emit yellow light.

In certain embodiments, the method comprises: disconnecting thedefective primary inorganic LEDs from the display circuit.

In certain embodiments, the method comprises: establishing an electricalconnection to a redundant inorganic LED in close proximity to each ofthe defective primary inorganic LEDs so that each of the redundantinorganic LEDs is connected to the display circuit.

In certain embodiments, establishing an electrical connection to each ofthe redundant LEDs comprises: directly and physically writing electricaltraces.

In certain embodiments, establishing an electrical connection to each ofsaid redundant LEDs comprises: placing a conductive jumper between eachof said redundant LEDs and the respective defective LED by microassembly. In certain embodiments, establishing an electrical connectionto each of the redundant LEDs comprises: establishing electricalconnection by solder reflow or contact between clean metal surfaces.

In certain embodiments, the method comprises prior to testing thedisplay, connecting each redundant inorganic LED to the display circuitin series with a resistor to form an LED-resistor pair such that eachLED-resistor pair is connected in parallel with a primary inorganic LED.

In certain embodiments, the method comprises: prior to testing thedisplay, connecting each redundant inorganic LED to the display circuitin series with a diode to form an LED-diode pair such that eachLED-diode pair is connected in parallel with a primary inorganic LED.

In certain embodiments, testing the display comprises: illuminating oneor more of the primary inorganic LEDs; and identifying defective primaryLEDs.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the plurality of printable inorganic LEDs aremicro transfer printed directly onto the display substrate.

In certain embodiments, each inorganic LED has a width from 2 to 5 μm, 5to 10 μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, eachinorganic LED has a length from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or20 to 50 μm. In certain embodiments, each inorganic LED has with aheight from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes the set of primary inorganic LEDs and theset of redundant inorganic LEDs, each LED has a light-emissive area, andthe combined light-emissive areas of LEDs is less than or equal toone-quarter of the contiguous display substrate area.

In certain embodiments, the combined light-emissive areas of the LEDs isless than or equal to one eighth, one tenth, one twentieth, onefiftieth, one hundredth, one five-hundredth, one thousandth, onetwo-thousandth, or one ten-thousandth of the contiguous displaysubstrate area.

In another aspect, the invention is directed to a micro-LED display,comprising: a display substrate that is at least partially transparent;an array of color-conversion structures on the display substrate, eachcolor-conversion structure comprising a color-conversion material; andan array of micro-LEDS separate from the color-conversion structures,each micro-LED in the array of micro-LEDs on a corresponding one of thecolor-conversion structure in the array of color-conversion structures.

In certain embodiments, the display substrate comprises an array ofrecesses in which the color-conversion materials are located.

In certain embodiments, the recesses are filled with thecolor-conversion materials.

In certain embodiments, the micro-LEDs are located over thecolor-conversion materials on a side of the color-conversion materialsopposite the display substrate so that most or all of the light emittedfrom the micro-LEDs emits downward through the color-conversion materialand the display substrate.

In certain embodiments, the method comprises one or more reflectivestructures substantially covering a side of the micro-LEDs opposite thedisplay substrate, so that the micro-LEDs reflect emitted light towardthe display substrates.

In certain embodiments, the one or more reflective structures comprisearray connection metals or micro-LED contacts.

In another aspect, the invention is directed to a micro-LED display,comprising: a display substrate; an array of micro-LEDS on the displaysubstrate; and an array of color-conversion structures separate from themicro-LED structures, each color-conversion structure in the array ofcolor-conversion structures on a corresponding one of the micro-LEDs inthe array of micro-LEDs, wherein each color-conversion structurecomprises a color-conversion material.

In certain embodiments, the color-conversion materials are on top of orat least partially surrounding the micro-LEDs on a side of themicro-LEDs opposite the display substrate.

In certain embodiments, the color-conversion materials comprisephosphor-bearing gels or resins, phosphor ceramics, or single-crystalphosphors. In certain embodiments, the color-conversion materials arechips of direct band gap semiconductors. In certain embodiments, thecolor-conversion materials are at least partially surrounding themicro-LEDs.

In certain embodiments, the display comprises supplementary mirrorstructures on the display substrate.

In certain embodiments, each micro-LED has an LED substrate separatefrom the display substrate.

In certain embodiments, the micro-LEDS are formed in a native substratedistinct and separate from the display substrate.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm. In certain embodiments, each micro-LED hasa width from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each micro-LED has a length from 2 to 5 μm, 5 to 10μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, each micro-LEDhas with a height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50μm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes the micro-LEDs, each micro-LED has alight-emissive area, and the combined light-emissive areas of themicro-LEDs is less than or equal to one-quarter of the contiguousdisplay substrate area.

In certain embodiments, the combined light-emissive areas of themicro-LEDs is less than or equal to one eighth, one tenth, onetwentieth, one fiftieth, one hundredth, one five-hundredth, onethousandth, one two-thousandth, or one ten-thousandth of the contiguousdisplay substrate area.

In certain embodiments, each micro-LED has an anode and a cathode on asame side of the respective micro-LED.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separated by a horizontal distance, wherein thehorizontal distance is from 100 nm to 500 nm, 500 nm to 1 micron, 1micron to 20 microns, 20 microns to 50 microns, or 50 microns to 100microns.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the array of micro-LEDs comprises a plurality ofred micro-LEDs that emit red light, a plurality of green micro-LEDs thatemit green light, and a plurality of blue micro-LEDs that emit bluelight, and each pixel comprises a red micro-LED of the plurality of redmicro-LEDs, a green micro-LED of the plurality of green micro-LEDs, anda blue micro-LED of the plurality of blue micro-LEDs.

In certain embodiments, the micro-LEDs are inorganic micro-LEDs.

In another aspect, the invention is directed to a method of microassembling a micro-LED light-emitter array, the method comprising:forming a plurality of micro-LEDs on a first substrate; providing adisplay substrate that is at least partially transparent; providing aplurality of color-conversion structures on the display substrate in anarray, each color-conversion structure comprising a color-conversionmaterial; micro assembling the plurality of micro-LEDs onto a displaysubstrate such that each micro-LED of the plurality of micro-LEDs is ona corresponding one of the color-conversion structures of the pluralityof color-conversion structures, wherein micro assembling the pluralityof micro-LEDs onto the display substrate comprises: contacting a portionof the plurality of micro-LEDs with a first transfer device having acontact surface, thereby temporarily binding the portion of theplurality of micro-LEDs to the contact surface such that the contactsurface has the portion of the plurality of micro-LEDs temporarilydisposed thereon; contacting the portion of the plurality of micro-LEDsdisposed on the contact surface of the first transfer device with aportion of the plurality of color-conversion structures; and separatingthe contact surface of the first transfer device and the portion of theplurality of micro-LEDs, wherein portion of the plurality of micro-LEDsare transferred onto the portion of color-conversion structures, therebyassembling the portion of the plurality of micro-LEDs on the portion ofthe color-conversion structures.

In certain embodiments, providing a plurality of color-conversionstructures located over the display substrate in an array comprises,prior to micro assembling the plurality of micro-LEDs onto a displaysubstrate: forming a plurality of recesses in the display substrate; andfilling the plurality of recesses with color-conversion materials overwhich the plurality of printable LEDs are printed.

In certain embodiments, providing a plurality of color-conversionstructures located over the display substrate in an array comprises,prior to micro assembling the plurality of micro-LEDs onto a displaysubstrate: micro assembling chips of color-conversion material onto thedisplay substrate.

In certain embodiments, the micro-LEDs are located over thecolor-conversion materials on a side of the color-conversion materialsopposite the display substrate so that most or all of the light emittedfrom the micro-LEDs emits downward through the color-conversion materialand the display substrate.

In certain embodiments, the method comprises one or more reflectivestructures substantially covering a side of the micro-LEDs opposite thedisplay substrate, so that the micro-LEDs reflect emitted light towardthe display substrates.

In certain embodiments, the one or more reflective structures comprisearray connection metals or micro-LED contacts.

In another aspect, the invention is directed to a method of microassembling a micro-LED light-emitter array, the method comprising:forming a plurality of micro-LEDs on a first substrate; providing adisplay substrate; micro assembling the plurality of micro-LEDs onto adisplay substrate, wherein micro assembling the plurality of micro-LEDsonto the display substrate comprises: contacting a portion of theplurality of micro-LEDs with a first transfer device having a contactsurface, thereby temporarily binding the portion of the plurality ofmicro-LEDs to the contact surface such that the contact surface has theportion of the plurality of micro-LEDs temporarily disposed thereon;contacting the portion of the plurality of micro-LEDs disposed on thecontact surface of the first transfer device with a portion of theplurality of color-conversion structures; separating the contact surfaceof the first transfer device and the portion of the plurality ofmicro-LEDs, wherein portion of the plurality of micro-LEDs aretransferred onto the portion of color-conversion structures, therebyassembling the portion of the plurality of micro-LEDs on the portion ofthe color-conversion structures; and providing a plurality ofcolor-conversion structures on the display substrate in an array suchthat each color-conversion structure of the plurality ofcolor-conversion structures is on a corresponding one of the micro-LEDof the plurality of micro-LEDs, wherein each color-conversion structurecomprises a color-conversion material.

In certain embodiments, the color-conversion materials are on top of orat least partially surrounding the micro-LEDs on a side of themicro-LEDs opposite the display substrate.

In certain embodiments, the color-conversion materials comprisephosphor-bearing gels or resins, phosphor ceramics, or single-crystalphosphors. In certain embodiments, the color-conversion materials arechips of direct band gap semiconductors. In certain embodiments, thecolor-conversion materials are at least partially surrounding themicro-LEDs.

In certain embodiments, the method comprises supplementary mirrorstructures on the display substrate.

In certain embodiments, each micro-LED has an LED substrate separatefrom the display substrate.

In certain embodiments, the micro-LEDS are formed in a native substratedistinct and separate from the display substrate.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm. In certain embodiments, each micro-LED hasa width from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each micro-LED has a length from 2 to 5 μm, 5 to 10μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, each micro-LEDhas with a height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50μm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes the micro-LEDs, each micro-LED has alight-emissive area, and the combined light-emissive areas of themicro-LEDs is less than or equal to one-quarter of the contiguousdisplay substrate area.

In certain embodiments, the combined light-emissive areas of themicro-LEDs is less than or equal to one eighth, one tenth, onetwentieth, one fiftieth, one hundredth, one five-hundredth, onethousandth, one two-thousandth, or one ten-thousandth of the contiguousdisplay substrate area.

In certain embodiments, each micro-LED has an anode and a cathode on asame side of the respective micro-LED.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separated by a horizontal distance, wherein thehorizontal distance is from 100 nm to 500 nm, 500 nm to 1 micron, 1micron to 20 microns, 20 microns to 50 microns, or 50 microns to 100microns.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the plurality of micro-LEDs comprises aplurality of red micro-LEDs that emit red light, a plurality of greenmicro-LEDs that emit green light, and a plurality of blue micro-LEDsthat emit blue light, and each pixel comprises a red micro-LED of theplurality of red micro-LEDs, a green micro-LED of the plurality of greenmicro-LEDs, and a blue micro-LED of the plurality of blue micro-LEDs.

In certain embodiments, the micro-LEDs are inorganic micro-LEDs.

In another aspect, the invention is directed to a multi-functionaldisplay, comprising: a display substrate; an array of micro-LEDs on thedisplay substrate; and an array of functional elements on the displaysubstrate, the micro-LEDs interlaced between the functional elements,wherein the display substrate is non-native to the micro-LEDs and thefunctional elements.

In certain embodiments, the functional elements are sensors ortransceivers. In certain embodiments, the functional elements compriseat least one member selected from the group consisting of: image capturedevices, optical sensors, photodiodes, infrared sensors, gesturesensors, infrared sensors, temperature sensors, power harvest devices,solar cells, motion energy scavenging devices, piezoelectric devices,capacitors, antennas, and wireless transmission devices.

In certain embodiments, the functional elements have a different spatialdensity over the display substrate than the micro-LEDs.

In certain embodiments, the micro-LEDs are formed in a native substrateseparate and distinct from the display substrate.

In certain embodiments, the functional elements are formed in a nativesubstrate separate and distinct from the display substrate. In certainembodiments, the number of functional elements is less than or equal tothe number of micro-LEDs in the display. In certain embodiments, thenumber of functional elements is less than or equal to one-third of thenumber of micro-LEDs in the display.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm.

In certain embodiments, each micro-LED has a width from 2 to 5 μm, 5 to10 μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, eachmicro-LED has a length from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to50 μm. In certain embodiments, each micro-LED has with a height from 2to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50 μm. In certainembodiments, each functional element has at least one of a width,length, and height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50μm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes the micro-LEDs, each micro-LED has alight-emissive area, and the combined light-emissive areas of themicro-LEDs is less than or equal to one-quarter of the contiguousdisplay substrate area.

In certain embodiments, the combined light-emissive areas of themicro-LEDs is less than or equal to one eighth, one tenth, onetwentieth, one fiftieth, one hundredth, one five-hundredth, onethousandth, one two-thousandth, or one ten-thousandth of the contiguousdisplay substrate area.

In certain embodiments, each micro-LED has an anode and a cathode on asame side of the respective micro-LED.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separated by a horizontal distance, wherein thehorizontal distance is from 100 nm to 500 nm, 500 nm to 1 micron, 1micron to 20 microns, 20 microns to 50 microns, or 50 microns to 100microns.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the array of micro-LEDs and the array offunctional elements are on a common plane.

In certain embodiments, the multi-functional display comprises aplurality of micro-integrated circuits, each micro-integrated circuitconnected to at least one micro-LED in the array of micro-LEDs and atleast one functional element in the array of functional elements.

In certain embodiments, the multi-functional display comprises: apolymer layer on the display substrate, wherein the array of micro-LEDsand the array of functional elements are on the polymer layer such thatthe polymer layer is between the display substrate and the array ofmicro-LEDs and the array of functional elements.

In certain embodiments, the multi-functional display comprises: a firstpatterned metal layer on a surface of the display substrate; adielectric layer on the display substrate and the first patterned metallayer, wherein the polymer layer is on the display substrate; aplurality of vias formed through the polymer and dielectric layer, eachvia associated with a corresponding micro-LED; and a second patternedmetal layer, the second patterned metal layer comprising a plurality ofanode interconnections and a plurality of cathode interconnections in asingle layer, each anode interconnection electrically connecting theanode of a corresponding micro-LED to the first patterned metal layerthrough a corresponding via of the plurality of vias and each cathodeinterconnections electrically contracting the cathode of a correspondingmicro-LED.

In certain embodiments, the multi-functional display comprises: aplurality of pixels, each pixel comprises at least one micro-LED in thearray of micro-LEDs and at least one functional element in the array offunctional elements.

In certain embodiments, the array of micro-LEDs comprises a plurality ofred micro-LEDs that emit red light, a plurality of green micro-LEDs thatemit green light, and a plurality of blue micro-LEDs that emit bluelight, and each pixel comprises a red micro-LED of the plurality of redmicro-LEDs, a green micro-LED of the plurality of green micro-LEDs, anda blue micro-LED of the plurality of blue micro-LEDs.

In certain embodiments, micro-LEDs are inorganic micro-LEDs.

In another aspect, the invention is directed to a method of microassembling a light emitting diode (LED) display interlaced withfunctional elements, the method comprising: forming a plurality ofmicro-LEDs on a first substrate; forming a plurality of functionalelements on a second substrate; micro assembling the plurality ofmicro-LEDs onto a display substrate, non-native to the plurality ofmicro-LEDs and the plurality of function elements, wherein microassembling the plurality of micro-LEDs onto the display substratecomprises: contacting a portion of the plurality of micro-LEDs with afirst transfer device having a contact surface, thereby temporarilybinding the portion of the plurality of micro-LEDs to the contactsurface such that the contact surface has the portion of the pluralityof micro-LEDs temporarily disposed thereon; contacting the portion ofthe plurality of micro-LEDs disposed on the contact surface of the firsttransfer device with a receiving surface of the display substrate;separating the contact surface of the first transfer device and theportion of the plurality of micro-LEDs, wherein portion of the pluralityof micro-LEDs are transferred onto the receiving surface, therebyassembling the portion of the plurality of micro-LEDs on the receivingsurface of the display substrate; and micro assembling the plurality offunctional elements onto a display substrate, comprising: contacting aportion of the plurality of functional elements of the portion of theplurality of functional elements with a second transfer device, therebybinding the portion of the plurality of functional elements to thecontact surface such that the contact surface has the portion of theplurality of functional elements disposed thereon; contacting theportion of the plurality of functional elements disposed on the contactsurface of the second transfer device with the receiving surface of thedisplay substrate; and separating the contact surface of the secondtransfer device and portion of the plurality of functional elements,wherein the portion of the plurality of functional elements istransferred onto the receiving surface of the display substrate, therebyassembling the portion of the plurality of functional elements on thereceiving surface of the display substrate.

In certain embodiments, the plurality of functional elements are sensorsor transceivers.

In certain embodiments, the plurality of functional elements comprise atleast one member selected from the group consisting of: image capturedevices, optical sensors, photodiodes, infrared sensors, gesturesensors, infrared sensors, temperature sensors, power harvest devices,solar cells, motion energy scavenging devices, piezoelectric devices,capacitors, antennas, and wireless transmission devices.

In certain embodiments, the plurality of functional elements have adifferent spatial density over the display substrate than themicro-LEDs.

In certain embodiments, the micro-LEDs are formed in a native substrateseparate and distinct from the display substrate.

In certain embodiments, the plurality of functional elements are formedin a native substrate separate and distinct from the display substrate.

In certain embodiments, the number of functional elements is less thanor equal to than the number of micro-LEDs in the display.

In certain embodiments, the number of functional elements is less thanor equal to than one-third of the number of micro-LEDs in the display.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm. In certain embodiments, each micro-LED hasa width from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each micro-LED has a length from 2 to 5 μm, 5 to 10μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, each micro-LEDhas with a height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50μm. In certain embodiments, each functional element has at least one ofa width, length, and height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or20 to 50 μm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the display substrate has a contiguous displaysubstrate area that includes the micro-LEDs, each micro-LED has alight-emissive area, and the combined light-emissive areas of themicro-LEDs is less than or equal to one-quarter of the contiguousdisplay substrate area.

In certain embodiments, the combined light-emissive areas of theplurality of light-emitting diodes is less than or equal to one eighth,one tenth, one twentieth, one fiftieth, one hundredth, onefive-hundredth, one thousandth, one two-thousandth, or oneten-thousandth of the contiguous display substrate area.

In certain embodiments, each micro-LED has an anode and a cathode on asame side of the respective micro-LED.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separated by a horizontal distance, wherein thehorizontal distance is from 100 nm to 500 nm, 500 nm to 1 micron, 1micron to 20 microns, 20 microns to 50 microns, or 50 microns to 100microns.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the plurality of micro-LEDs and the plurality offunctional elements are on a common plane.

In certain embodiments, the method comprises: a plurality ofmicro-integrated circuits, each micro-integrated circuit connected to atleast one micro-LED in the plurality of micro-LEDs and at least onefunctional element of plurality of functional elements.

In certain embodiments, the method comprises: a polymer layer on thedisplay substrate, wherein the plurality of micro-LEDs and the pluralityof functional elements are on polymer layer such that the polymer layeris between the display substrate and the plurality of micro-LEDs and theplurality of functional elements.

In certain embodiments, the method comprises: a first patterned metallayer on a surface of the display substrate; a dielectric layer on thedisplay substrate and the first patterned metal layer, wherein thepolymer layer is on the display substrate; a plurality of vias formedthrough the polymer and dielectric layer, each via associated with acorresponding micro-LED; and

a second patterned metal layer, the second patterned metal layercomprising a plurality of anode interconnections and a plurality ofcathode interconnections in a single layer, each anode interconnectionelectrically connecting the anode of a corresponding micro-LED to thefirst patterned metal layer through a corresponding via of the pluralityof vias and each cathode interconnections electrically contracting thecathode of a corresponding micro-LED.

In certain embodiments, the method comprises: a plurality of pixels,each pixel comprises at least one micro-LED in the plurality ofmicro-LEDs and at least one functional element in the plurality offunctional elements.

In certain embodiments, the plurality of micro-LEDs comprises aplurality of red micro-LEDs that emit red light, a plurality of greenmicro-LEDs that emit green light, and a plurality of blue micro-LEDsthat emit blue light, and each pixel comprises a red micro-LED of theplurality of red micro-LEDs, a green micro-LED of the plurality of greenmicro-LEDs, and a blue micro-LED of the plurality of blue micro-LEDs.

In certain embodiments, the micro-LEDs are inorganic micro-LEDs.

In certain embodiments, the second transfer device is the first transferdevice.

In certain embodiments, the first transfer device comprises an elastomerstamp.

In another aspect, the invention is directed to a multi-mode display,comprising: a display substrate; a first emissive inorganic micro-LEDdisplay formed over the display substrate; and a second display formedover the display substrate, the second display of a different type thanthe first emissive micro-LED display.

In certain embodiments, the second display is a non-emissive reflectivedisplay. In certain embodiments, the second display is anelectrophoretic or MEMs-based display.

In certain embodiments, the first display comprises a plurality of firstpixels and the second display comprises a plurality of second pixels,wherein each of the plurality of first pixels is smaller than each ofthe plurality of second pixels.

In certain embodiments, the multi-mode display comprises a controllerfor switching between the first display and the second display.

In certain embodiments, the multi-mode display comprises a cell phone, asmart phone, or a tablet computing device.

In certain embodiments, the first display is located over a differentportion of the display substrate than the second display.

In certain embodiments, the first display and the second display arelocated over a same portion of the display substrate. In certainembodiments, the first display is located on top of the second displayon a side of the second display opposite the display substrate.

In certain embodiments, light-controlling elements of the first displayare interlaced on the display substrate with light-controlling elementsof the second display.

In certain embodiments, the micro-LEDS are formed in an native substratedistinct and separate from the display substrate.

In certain embodiments, the first display and the second display areformed on the display substrate. In certain embodiments, the firstdisplay is on a first side of the display substrate and the seconddisplay is on a second side of the display substrate, opposite the firstside.

In certain embodiments, the second display is on the display substrateand the first display is on a micro-LED display substrate, separate fromthe display substrate and located over the display substrate.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm. In certain embodiments, each micro-LED hasa width from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each micro-LED has a length from 2 to 5 μm, 5 to 10μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, each micro-LEDhas with a height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50μm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light. In certainembodiments, the display substrate has a contiguous display substratearea that includes the micro-LEDs, each micro-LED has a light-emissivearea, and the combined light-emissive areas of the micro-LEDs is lessthan or equal to one-quarter of the contiguous display substrate area.

In certain embodiments, the combined light-emissive areas of themicro-LEDs is less than or equal to one eighth, one tenth, onetwentieth, one fiftieth, one hundredth, one five-hundredth, onethousandth, one two-thousandth, or one ten-thousandth of the contiguousdisplay substrate area.

In certain embodiments, each micro-LED has an anode and a cathode on asame side of the respective micro-LED.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separated by a horizontal distance, wherein thehorizontal distance is from 100 nm to 500 nm, 500 nm to 1 micron, 1micron to 20 microns, 20 microns to 50 microns, or 50 microns to 100microns.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the first emissive micro-LED display comprise aplurality of red micro-LEDs that emit red light, a plurality of greenmicro-LEDs that emit green light, and a plurality of blue micro-LEDsthat emit blue light, and each pixel of the first emissive micro-LEDdisplay comprises a red micro-LED of the plurality of red micro-LEDs, agreen micro-LED of the plurality of green micro-LEDs, and a bluemicro-LED of the plurality of blue micro-LEDs.

In certain embodiments, the micro-LEDs are inorganic micro-LEDs.

In certain embodiments, the first emissive inorganic micro-LED displaycomprises a plurality of inorganic micro-LEDs formed in an LED substrateseparate and distinct from the display substrate and the second displayis formed on or in and is native to the display substrate, wherein theLED substrate is adhered to the display substrate.

In another aspect, the invention is directed to a method of microassembling a micro-LED light-emitter array, the method comprising:forming a plurality of micro-LEDs on a first substrate; providing adisplay substrate; micro assembling the plurality of micro-LEDs over thedisplay substrate, thereby forming a first emissive micro-LED displayover the display substrate; and forming a second display over thedisplay substrate, the second display of a different type than the firstemissive micro-LED display.

In certain embodiments, the second display is a non-emissive reflectivedisplay.

In certain embodiments, the second display is an electrophoretic orMEMs-based display.

In certain embodiments, the first display comprises a plurality of firstpixels and the second display comprises a plurality of second pixels,wherein each of the plurality of first pixels is smaller than each ofthe plurality of second pixels.

In certain embodiments, the method further comprises a controller forswitching between the first display and the second display.

In certain embodiments, the method further comprises a cell phone, asmart phone, or a tablet computing device.

In certain embodiments, the first display is located over a differentportion of the display substrate than the second display. In certainembodiments, the first display and the second display are located over asame portion of the display substrate. In certain embodiments, the firstdisplay is located on top of the second display on a side of the seconddisplay opposite the display substrate.

In certain embodiments, light-controlling elements of the first displayare interlaced on the display substrate with light-controlling elementsof the second display.

In certain embodiments, the micro-LEDS are formed in an native substratedistinct and separate from the display substrate.

In certain embodiments, the first display and the second display areformed on the display substrate.

In certain embodiments, the first display is on a first side of thedisplay substrate and the second display is on a second side of thedisplay substrate, opposite the first side.

In certain embodiments, the second display is on the display substrateand the first display is on a micro-LED display substrate, separate fromthe display substrate and located over the display substrate.

In certain embodiments, the display substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm. In certain embodiments, each micro-LED hasa width from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. Incertain embodiments, each micro-LED has a length from 2 to 5 μm, 5 to 10μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, each micro-LEDhas with a height from 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50μm.

In certain embodiments, a resolution of the display is 120×90,1440×1080, 1920×1080, 1280×720, 3840×2160, 7680×4320, or 15360×8640.

In certain embodiments, the display substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light. In certainembodiments, the display substrate has a contiguous display substratearea that includes the micro-LEDs, each micro-LED has a light-emissivearea, and the combined light-emissive areas of the micro-LEDs is lessthan or equal to one-quarter of the contiguous display substrate area.

In certain embodiments, the combined light-emissive areas of themicro-LEDs is less than or equal to one eighth, one tenth, onetwentieth, one fiftieth, one hundredth, one five-hundredth, onethousandth, one two-thousandth, or one ten-thousandth of the contiguousdisplay substrate area.

In certain embodiments, each micro-LED has an anode and a cathode on asame side of the respective micro-LED.

In certain embodiments, the anode and cathode of a respective lightemitter are horizontally separated by a horizontal distance, wherein thehorizontal distance is from 100 nm to 500 nm, 500 nm to 1 micron, 1micron to 20 microns, 20 microns to 50 microns, or 50 microns to 100microns.

In certain embodiments, the display substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the plurality of micro-LEDs comprises aplurality of red micro-LEDs that emit red light, a plurality of greenmicro-LEDs that emit green light, and a plurality of blue micro-LEDsthat emit blue light, and each pixel comprises a red micro-LED of theplurality of red micro-LEDs, a green micro-LED of the plurality of greenmicro-LEDs, and a blue micro-LED of the plurality of blue micro-LEDs.

In certain embodiments, the micro-LEDs are inorganic micro-LEDs.

In another aspect, the invention is directed to a micro assembleddevice, comprising: a device substrate; a first electrical conductor onthe device substrate; a second electrical conductor on the devicesubstrate; a conductive jumper element distinct and separate from thedevice substrate having one or more jumper conductors; and wherein theconductive jumper element is on the device substrate with the firstjumper conductor of the one or more jumper conductors in electricalcontact with the first electrical conductor and the second electricalconductor.

In certain embodiments, the conductive jumper element is a conductivepassive device.

In certain embodiments, the conductive jumper element is an activedevice. In certain embodiments, the active device is a CMOS device. Incertain embodiments, the active device comprises at least one of drivecircuitry and non-volatile memory.

In certain embodiments, the conductive jumper element is housed within astructure suitable for micro transfer printing. In certain embodiments,the conductive jumper element comprises one or more of a semiconductor,silicon, silicon on insulator, glass, metal, and a dielectric.

In certain embodiments, the jumper conductor comprises a semiconductor,a metal, a noble metal, gold, silver, platinum, copper, stainless steel,nickel, chromium, solder, PbSn, AgSn, or AgSn.

In certain embodiments, a portion of the conductive jumper elementadjacent to the conductor substrate is recessed.

In certain embodiments, the device comprises a third electricalconductor on the conductor substrate that is electrically isolated fromthe first electrical conductor and the second electrical conductor,wherein the third electrical conductor is located under the recess ofthe conductive jumper element.

In certain embodiments, the recess comprises an exposed insulator.

In certain embodiments, the conductive jumper element comprises a firstterminal electrically connected to a second terminal with an exposedinsulator there between, wherein the first terminal, second terminal,and the exposed insulator form a planar surface on at least one side ofthe conductive jumper element.

In certain embodiments, the device comprises a third electricalconductor on the conductor substrate that is electrically isolated fromthe first electrical conductor and the second electrical conductor,wherein the third electrical conductor that is contacted by the exposedinsulator.

In certain embodiments, a portion of at least one of the jumperconductors is covered with an insulator.

In certain embodiments, a central portion of at least one of the jumperconductors is covered with an insulator separating exposed ends of thejumper conductor.

In certain embodiments, the substrate is a display substrate and theconductive jumper element electrically connects a redundant lightemitter to a display circuit.

In certain embodiments, the redundant light emitter is connected to thedisplay circuit in place of a defective primary light emitter.

In certain embodiments, a distance between the first electricalconductor and the second electrical conductor is from 100 nm to 500 nm,500 nm to 1 micron, 1 micron to 20 microns, 20 microns to 50 microns, or50 microns to 100 microns. In certain embodiments, the device substratehas a thickness from 5 to 10 microns, 10 to 50 microns, 50 to 100microns, 100 to 200 microns, 200 to 500 microns, 500 microns to 0.5 mm,0.5 to 1 mm, 1 mm to 5 mm, 5 mm to 10 mm, or 10 mm to 20 mm.

In certain embodiments, the conductive jumper element has a width from 2to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. In certainembodiments, the conductive jumper element has a length from 2 to 5 μm,5 to 10 μm, 10 to 20 μm, or 20 to 50 μm. In certain embodiments, theconductive jumper element has with a height from 2 to 5 μm, 4 to 10 μm,10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the device substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light. In certainembodiments, the device substrate is a member selected from the groupconsisting of polymer, plastic, resin, polyimide, PEN, PET, metal, metalfoil, glass, a semiconductor, and sapphire.

In certain embodiments, the conductive jumper element is a cross-over.

In certain embodiments, the device comprises: a plurality of firstelectrical conductors on the device substrate, wherein the plurality offirst electrical conductors comprises the first electrical conductor; aplurality of second electrical conductors on the device substrate,wherein the plurality of second electrical conductors comprises thesecond electrical conductor; a conductive jumper element distinct andseparate from the device substrate having a plurality of jumperconductors, wherein the plurality of jumper conductors comprises the oneor more jumper conductors; and each jumper conductor of the plurality ofjumper conductors in electrical contact with a first electricalconductor of the plurality of electrical conductors and a secondelectrical conductor of the plurality of second electrical conductors.

In another aspect, the invention is directed to a method of providing amicro assembled device, comprising: providing a device comprising adevice substrate; a first electrical conductor on the device substrate;a second electrical conductor on the device substrate; and microassembling a conductive jumper element having one or more jumperconductors on the device substrate, wherein the conductive jumperelement is on the device substrate with the first jumper conductor ofthe one or more jumper conductors in electrical contact with the firstelectrical conductor and the second electrical conductor.

In certain embodiments, the conductive jumper element is a conductivepassive device. In certain embodiments, the conductive jumper element isan active device. In certain embodiments, the active device is a CMOSdevice. In certain embodiments, the active device comprises at least oneof drive circuitry and non-volatile memory.

In certain embodiments, the conductive jumper element is housed within astructure suitable for micro transfer printing.

In certain embodiments, the conductive jumper element comprises one ormore of a semiconductor, silicon, silicon on insulator, glass, metal,and a dielectric.

In certain embodiments, the jumper conductor comprises a semiconductor,a metal, a noble metal, gold, silver, platinum, copper, stainless steel,nickel, chromium, solder, PbSn, AgSn, or AgSn.

In certain embodiments, a portion of the conductive jumper elementadjacent to the conductor substrate is recessed.

In certain embodiments, a third electrical conductor on the conductorsubstrate that is electrically isolated from the first electricalconductor and the second electrical conductor, wherein the thirdelectrical conductor is located under the recess of the conductivejumper element.

In certain embodiments, the recess comprises an exposed insulator.

In certain embodiments, the conductive jumper element comprises a firstterminal electrically connected to a second terminal with an exposedinsulator there between, wherein the first terminal, second terminal,and the exposed insulator form a planar surface on at least one side ofthe conductive jumper element.

In certain embodiments, the method comprises a third electricalconductor on the conductor substrate that is electrically isolated fromthe first electrical conductor and the second electrical conductor,wherein the third electrical conductor that is contacted by the exposedinsulator.

In certain embodiments, a portion of at least one of the jumperconductors is covered with an insulator.

In certain embodiments, a central portion of at least one of the jumperconductors is covered with an insulator separating exposed ends of thejumper conductor.

In certain embodiments, the substrate is a display substrate and theconductive jumper element electrically connects a redundant lightemitter to a display circuit.

In certain embodiments, the redundant light emitter is connected to thedisplay circuit in place of a defective primary light emitter.

In certain embodiments, a distance between the first electricalconductor and the second electrical conductor is from 100 nm to 500 nm,500 nm to 1 micron, 1 micron to 20 microns, 20 microns to 50 microns, or50 microns to 100 microns.

In certain embodiments, the device substrate has a thickness from 5 to10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mmto 10 mm, or 10 mm to 20 mm.

In certain embodiments, the conductive jumper element has a width from 2to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the conductive jumper element has a length from2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the conductive jumper element has with a heightfrom 2 to 5 μm, 4 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In certain embodiments, the device substrate has a transparency greaterthan or equal to 50%, 80%, 90%, or 95% for visible light.

In certain embodiments, the device substrate is a member selected fromthe group consisting of polymer, plastic, resin, polyimide, PEN, PET,metal, metal foil, glass, a semiconductor, and sapphire.

In certain embodiments, the conductive jumper element is a cross-over.

In certain embodiments, the method comprises: a plurality of firstelectrical conductors on the device substrate, wherein the plurality offirst electrical conductors comprises the first electrical conductor; aplurality of second electrical conductors on the device substrate,wherein the plurality of second electrical conductors comprises thesecond electrical conductor; a conductive jumper element distinct andseparate from the device substrate having a plurality of jumperconductors, wherein the plurality of jumper conductors comprises the oneor more jumper conductors; and each jumper conductor of the plurality ofjumper conductors in electrical contact with a first electricalconductor of the plurality of electrical conductors and a secondelectrical conductor of the plurality of second electrical conductors.

In certain embodiments, micro assembling the conductive jumper elementcomprises: contacting the conductive jumper element with a transferdevice having a contact surface, thereby temporarily binding theconductive jumper element to the contact surface such that the contactsurface has the conductive jumper element temporarily disposed thereon;contacting the conductive jumper element disposed on the contact surfaceof the transfer device with a receiving surface of the device substrate;and separating the contact surface of the transfer device and theconductive jumper element, wherein conductive jumper element istransferred onto the receiving surface, thereby assembling the portionof the conductive jumper element on the receiving surface of the devicesubstrate.

In certain embodiments, the transfer device comprises an elastomerstamp.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, aspects, features, and advantages ofthe present disclosure will become more apparent and better understoodby referring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is an illustration of a typical pixel used in an LCD display;

FIG. 2 is an illustration of an example pixel constructed in accordancewith the disclosed technology;

FIG. 3 is a micrograph of small micro-LEDs assembled using microassembly on display substrates;

FIG. 4 is an illustration of an example micro-LED display that includesredundant RGB inorganic micro-LEDs, according to an illustrativeembodiment of the invention;

FIG. 5 is an illustration of an example pixel in accordance with thedisclosed technology;

FIG. 6 is an illustration of an example pixel of a display with amissing micro-LED, according to an illustrative embodiment of theinvention;

FIG. 7 is an illustration of a micro-assembled display that includesredundant RGB inorganic micro-LEDs, a driver IC, and micro-sensors,according to an illustrative embodiment of the invention;

FIGS. 8A through 8D are illustrations of redundant micro-LEDs in amicro-LED panel for micro-assembled displays and lighting elements,according to an illustrative embodiment of the invention;

FIGS. 9A through 9C are schematics that illustrate a micro-transferprinted array of micro-LEDs on glass, according to an illustrativeembodiment of the invention;

FIG. 10 is an illustration of an example structure for repairingmicro-LED array devices using micro-assembled jumpers, according to anillustrative embodiment of the invention;

FIGS. 11A and 11B illustrate micro-assembled cross-overs for layerreduction in micro-LED array devices, according to an illustrativeembodiment of the invention;

FIGS. 12A and 12B are illustrations of example circuits using a resistorand a diode to facilitate repair by providing an electrical signature ofa redundant micro-assembled micro-LED pixel or sub-pixel in a lightingelement or display, according to an illustrative embodiment of theinvention;

FIG. 13 illustrates electrical connectors suitable for micro assembly,according to an illustrative embodiment of the invention;

FIG. 14 is an illustration of a micro-assembled display that includessupplementary RGB inorganic micro-LEDs, according to an illustrativeembodiment of the invention;

FIGS. 15A and 15B are illustrations of micro-assembled micro-LED displayand lighting element architectures, according to an illustrativeembodiment of the invention;

FIG. 16 illustrates a micro-assembled micro-LED display and lightingelement architecture, according to an illustrative embodiment of theinvention;

FIG. 17 is an illustration of an example display formed by twoindependent displays occupying the same viewable area, according to anillustrative embodiment of the invention;

FIG. 18 is an illustration of a stacked micro-LED display, according toan illustrative embodiment of the invention;

FIG. 19 is an illustration of a micro-assembled stacked display formedof three display panels, according to an illustrative embodiment of theinvention;

FIG. 20 is an illustration of a stacked display formed by two individualdisplays with different resolutions, according to an illustrativeembodiment of the invention;

FIG. 21 is an illustration of an example pixel of a multi-mode display,according to an illustrative embodiment of the invention;

FIG. 22 is an illustration of an example pixel of a multi-mode display,according to an illustrative embodiment of the invention;

FIG. 23 is an illustration of a pixel with an integrated circuitconnected to redundant micro-LEDs and a micro-sensor, according to anillustrative embodiment of the invention;

FIG. 24 is an example illustration of the color gamut of human visionand an HDTV, according to an illustrative embodiment of the invention;

FIG. 25 is an illustration of an example pixel with improved colorgamut, according to an illustrative embodiment of the invention;

FIG. 26 is an illustration of an example pixel for use in amicro-assembled inorganic micro-LED array for yielding visually perfectdevices, according to an illustrative embodiment of the invention;

FIGS. 27A and 27B are illustrations of two micro-assembled inorganicmicro-LED array strategies for yielding visually perfect devices,according to an illustrative embodiment of the invention;

FIG. 28 is an illustration of an example pixel prior to connection,according to an illustrative embodiment of the invention;

FIG. 29 is an illustration of implementing color conversion inmicro-assembled micro-LED displays and lighting elements usingcolor-conversion material, according to an illustrative embodiment ofthe invention;

FIGS. 30A and 30B are a micrograph and illustration, respectively, ofdevices using self-aligned dielectrics for micro-assembled micro-LEDdisplays and lighting elements, according to an illustrative embodimentof the invention;

FIG. 31 is an illustration of an example 4×4 array of function elementscontrolled by a single micro-assembled integrated circuit, according toan illustrative embodiment of the invention;

FIG. 32 illustrates an example device including several 4×4 arrays offunction elements each controlled by a single micro-assembled integratedcircuit, according to an illustrative embodiment of the invention;

FIG. 33 is an illustration of an example array using control elements tocontrol different types of functional elements, according to anillustrative embodiment of the invention;

FIG. 34 is an illustration of a display formed using micro assembly withintegrated circuit pixel clusters that can each act as an independentdisplay, according to an illustrative embodiment of the invention;

FIG. 35 is an illustration of an example in which a user has selected toturn on just a portion of the overall device, according to anillustrative embodiment of the invention;

FIG. 36 is an illustration of an example in which a user has selected toturn on just a portion of the overall device in a non-standard shape,according to an illustrative embodiment of the invention;

FIG. 37 is an illustration of an example array with wireless data and/orpower input, according to an illustrative embodiment of the invention;

FIG. 38 is an illustration of a control element designed to havebuilt-in redundancy, according to an illustrative embodiment of theinvention;

FIG. 39 is an illustration of an array with a control device withbuilt-in memory, according to an illustrative embodiment of theinvention;

FIG. 40 is an illustration of a micro-assembled micro-LED display withmicro-assembled temperature sensing elements, according to anillustrative embodiment of the invention;

FIG. 41 is an image of a passive-matrix inorganic light-emitting diodedisplay, according to an illustrative embodiment of the invention,according to an illustrative embodiment of the invention;

FIG. 42 is an optical micrograph of a pixel within the display,according to an illustrative embodiment of the invention, according toan illustrative embodiment of the invention;

FIG. 43 is an optical micrograph of a single pixel within the display,according to an illustrative embodiment of the invention, according toan illustrative embodiment of the invention;

FIG. 44 is an image of the completed display substrate withpassive-matrix displays thereon, according to an illustrative embodimentof the invention, according to an illustrative embodiment of theinvention;

FIG. 45 is an optical micrograph of the pixel array of the display,according to an illustrative embodiment of the invention, according toan illustrative embodiment of the invention;

FIG. 46 is a flow chart of a method for manufacturing a passive-matrixinorganic light-emitting diode display, according to an illustrativeembodiment of the invention;

FIG. 47A is an image of a passive matrix inorganic light-emitting diodedisplay, according to an illustrative embodiment of the invention;

FIG. 47B is a close up image of the passive matrix-inorganiclight-emitting diode display of FIG. 47A, according to an illustrativeembodiment of the invention;

FIG. 48A is an image of the passive matrix inorganic light-emittingdiode display, according to an illustrative embodiment of the invention;

FIG. 48B is a close up image of the passive matrix inorganiclight-emitting diode display of FIG. 48A, according to an illustrativeembodiment of the invention;

FIGS. 49A-49G are images showing that the display is partiallytransparent, according to an illustrative embodiment of the invention;

FIG. 50 is an optical micrograph of example printed LEDs wired in apassive-matrix configuration;

FIG. 51 is a schematic and optical micrograph of example printed LEDswired in a passive-matrix configuration;

FIG. 52 is an optical micrograph of a single LED wired in apassive-matrix configuration;

FIGS. 53A and 53B are a plan view and a cross section, respectively, ofan example architecture of a micro-LED suitable for contacting bothterminals from one face of the LED; and

FIGS. 54A-54E are schematic cross-sections of example architectures ofmicro-LEDs.

The features and advantages of the present disclosure will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

DETAILED DESCRIPTION

As used herein the expression “semiconductor element” and “semiconductorstructure” are used synonymously and broadly refer to a semiconductormaterial, structure, device, or component of a device. Semiconductorelements include high-quality single crystalline and polycrystallinesemiconductors, semiconductor materials fabricated via high-temperatureprocessing, doped semiconductor materials, organic and inorganicsemiconductors, and composite semiconductor materials and structureshaving one or more additional semiconductor components and/ornon-semiconductor components, such as dielectric layers or materialsand/or conducting layers or materials. Semiconductor elements includesemiconductor devices and device components including, but not limitedto, transistors, photovoltaics including solar cells, diodes,light-emitting diodes, lasers, p-n junctions, photodiodes, integratedcircuits, and sensors. In addition, semiconductor element can refer to apart or portion that forms an functional semiconductor device orproduct.

“Semiconductor” refers to any material that is a material that is aninsulator at a very low temperature, but which has an appreciableelectrical conductivity at temperatures of about 300 Kelvin. Theelectrical characteristics of a semiconductor can be modified by theaddition of impurities or dopants and controlled by the use ofelectrical fields. In the present description, use of the termsemiconductor is intended to be consistent with use of this term in theart of microelectronics and electronic devices. Semiconductors useful inthe present invention can include elemental semiconductors, such assilicon, germanium and diamond, and compound semiconductors, for examplegroup IV compound semiconductors such as SiC and SiGe, group III-Vsemiconductors such as AlSb, AlAs, Aln, AlP, BN, GaSb, GaAs, GaN, GaP,InSb, InAs, InN, and InP, group III-V ternary semiconductors alloys suchas Al_(x)Ga1-_(x)As, group II-VI semiconductors such as CsSe, CdS, CdTe,ZnO, ZnSe, ZnS, and ZnTe, group I-VII semiconductors CuCl, group IV-VIsemiconductors such as PbS, PbTe and SnS, layer semiconductors such asPbI₂, MoS₂ and GaSe, oxide semiconductors such as CuO and Cu₂O. The termsemiconductor includes intrinsic semiconductors and extrinsicsemiconductors that are doped with one or more selected materials,including semiconductor having p-type doping materials and n-type dopingmaterials, to provide beneficial electronic properties useful for agiven application or device. The term semiconductor includes compositematerials comprising a mixture of semiconductors and/or dopants.Specific semiconductor materials useful for in some applications of thepresent invention include, but are not limited to, Si, Ge, SiC, AlP,AlAs, AlSb, GaN, GaP, GaAs, GaSb, InP, InAs, GaSb, InP, InAs, InSb, ZnO,ZnSe, ZnTe, CdS, CdSe, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, PbS, PbSe,PbTe, AlGaAs, AlInAs, AlInP, GaAsP, GaInAs, GaInP, AlGaAsSb, AlGaInP,and GaInAsP. Porous silicon semiconductor materials are useful forapplications of the present invention in the field of sensors andlight-emitting materials, such as light-emitting diodes (LEDs) andsolid-state lasers. Impurities of semiconductor materials are atoms,elements, ions or molecules other than the semiconductor material(s)themselves or any dopants provided in the semiconductor material.Impurities are undesirable materials present in semiconductor materialsthat can negatively impact the electronic properties of semiconductormaterials, and include but are not limited to oxygen, carbon, and metalsincluding heavy metals. Heavy-metal impurities include, but are notlimited to, the group of elements between copper and lead on theperiodic table, calcium, sodium, and all ions, compounds and/orcomplexes thereof.

“Substrate” refers to a structure or material on which, or in which, aprocess is (or has been) conducted, such as patterning, assembly orintegration of semiconductor elements. Substrates include, but are notlimited to: (i) a structure upon which semiconductor elements arefabricated, deposited, transferred or supported (also referred to as anative substrate); (ii) a device substrate, for example an electronicdevice substrate; (iii) a donor substrate having elements, such assemiconductor elements, for subsequent transfer, assembly orintegration; and (iv) a target substrate for receiving printablestructures, such as semiconductor elements. A donor substrate can be,but is not necessarily, a native substrate.

“Display substrate” as used herein refers to the target substrate (e.g.,non-native substrate) for receiving printable structures, such assemiconductor elements. Examples of display substrate materials includepolymer, plastic, resin, polyimide, polyethylene naphthalate,polyethylene terephthalate, metal, metal foil, glass, flexible glass, asemiconductor, and sapphire.

The terms “micro” and “micro-device” as used herein refer to thedescriptive size of certain devices or structures in accordance withembodiments of the invention. As used herein, the terms “micro” and“micro-device” are meant to refer to structures or devices on the scaleof 0.5 to 250 μm. However, it is to be appreciated that embodiments ofthe present invention are not necessarily so limited, and that certainaspects of the embodiments can be applicable to larger or smaller sizescales.

As used herein, “micro-LED” refers to an inorganic light-emitting diodeon the scale of 0.5 to 250 μm. For example, micro-LEDs can have at leastone of a width, length, and height (or two or all three dimensions) from0.5 to 2 μm, 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, 20 to 50 μm, 20 to 50μm, 50 to 100 μm, or 100 to 250 μm. Micro-LEDs emit light whenenergized. The color of the light emitted by an LED varies dependingupon the structure of the micro-LED. For example, when energized a redmicro-LED emits red light, a green micro-LED emits green light, a bluemicro-LED emits blue light, a yellow micro-LED emits yellow light, and acyan micro-LED emits cyan light.

“Printable” relates to materials, structures, device components, orintegrated functional devices that are capable of transfer, assembly,patterning, organizing, or integrating onto or into substrates withoutexposure of the substrate to high temperatures (e.g. At temperaturesless than or equal to about 400, 200, or 150 degrees Celsius). In oneembodiment of the present invention, printable materials, elements,device components, or devices are capable of transfer, assembly,patterning, organizing and/or integrating onto or into substrates viasolution printing, micro-transfer printing, or dry transfer contactprinting.

“Printable semiconductor elements” of the present invention comprisesemiconductor structures that can be assembled or integrated ontosubstrate surfaces, for example by using dry transfer contact printing,micro-transfer printing, or solution printing methods. In oneembodiment, printable semiconductor elements of the present inventionare unitary single crystalline, polycrystalline or microcrystallineinorganic semiconductor structures. In the context of this description,a unitary structure is a monolithic element having features that aremechanically connected. Semiconductor elements of the present inventioncan be undoped or doped, can have a selected spatial distribution ofdopants and can be doped with a plurality of different dopant materials,including p- and n-type dopants. The present invention includesmicrostructured printable semiconductor elements having at least onecross-sectional dimension greater than or equal to about 1 micron andnanostructured printable semiconductor elements having at least onecross-sectional dimension less than or equal to about 1 micron.Printable semiconductor elements useful in many applications compriseelements derived from “top down” processing of high-purity bulkmaterials, such as high-purity crystalline semiconductor wafersgenerated using conventional high-temperature processing techniques. Inone embodiment, printable semiconductor elements of the presentinvention comprise composite structures having a semiconductoroperationally connected to at least one additional device component orstructure, such as a conducting layer, dielectric layer, electrode,additional semiconductor structure, or any combination of these. In oneembodiment, printable semiconductor elements of the present inventioncomprise stretchable semiconductor elements or heterogeneoussemiconductor elements.

The term “flexible” refers to the ability of a material, structure,device or device component to be reversibly deformed into a curvedshape, e.g., without undergoing a transformation that introducessignificant strain, such as strain characterizing the failure point of amaterial, structure, device, or device component.

“Plastic” refers to any synthetic or naturally occurring material orcombination of materials that can be molded or shaped, generally whenheated, and hardened into a desired shape. Exemplary plastics useful inthe devices and methods of the present invention include, but are notlimited to, polymers, resins and cellulose derivatives. In the presentdescription, the term plastic is intended to include composite plasticmaterials comprising one or more plastics with one or more additives,such as structural enhancers, fillers, fibers, plasticizers, stabilizersor additives which can provide desired chemical or physical properties.“Dielectric” and “dielectric material” are used synonymously in thepresent description and refer to a substance that is highly resistant toflow of electric current and can be polarized by an applied electricfield. Useful dielectric materials include, but are not limited to,SiO₂, Ta₂O₅, TiO₂, ZrO₂, Y₂O₃, SiN₄, STO, BST, PLZT, PMN, and PZT.

“Polymer” refers to a molecule comprising a plurality of repeatingchemical groups, typically referred to as monomers. Polymers are oftencharacterized by high molecular masses. Polymers useable in the presentinvention can be organic polymers or inorganic polymers and can be inamorphous, semi-amorphous, crystalline or partially crystalline states.Polymers can comprise monomers having the same chemical composition orcan comprise a plurality of monomers having different chemicalcompositions, such as a copolymer. Cross-linked polymers having linkedmonomer chains are particularly useful for some applications of thepresent invention. Polymers useable in the methods, devices and devicecomponents of the present invention include, but are not limited to,plastics, elastomers, thermoplastic elastomers, elastoplastics,thermostats, thermoplastics and acrylates. Exemplary polymers include,but are not limited to, acetal polymers, biodegradable polymers,cellulosic polymers, fluoropolymers, nylons, polyacrylonitrile polymers,polyamide-imide polymers, polyimides, polyarylates, polybenzimidazole,polybutylene, polycarbonate, polyesters, polyetherimide, polyethylene,polyethylene copolymers and modified polyethylenes, polyketones,poly(methyl methacrylate, polymethylpentene, polyphenylene oxides andpolyphenylene sulfides, polyphthalamide, polypropylene, polyurethanes,styrenic resins, sulphone based resins, vinyl-based resins or anycombinations of these.

“Micro-transfer printing” as used herein refers to systems, methods, andtechniques for the deterministic assembly of micro- and nano-materials,devices, and semiconductor elements into spatially organized, functionalarrangements with two-dimensional and three-dimensional layouts. It isoften difficult to pick up and place ultra-thin or small devices,however, micro-transfer printing permits the selection and applicationof these ultra-thin, fragile, or small devices, such as micro-LEDs,without causing damage to the devices themselves. Microstructured stamps(e.g., elastomeric, electrostatic stamps, or hybridelastomeric/electrostatic stamps) can be used to pick up micro devices,transport the micro devices to a destination substrate, and print themicro devices onto the destination substrate. In some embodiments,surface adhesion forces are used to control the selection and printingof these devices onto the destination substrate. This process can beperformed massively in parallel. The stamps can be designed to transfera single device or hundreds to thousands of discrete structures in asingle pick-up-and-print operation. For a discussion of micro-transferprinting generally, see U.S. Pat. Nos. 7,622,367 and 8,506,867, each ofwhich is hereby incorporated by reference in its entirety.

Micro-transfer printing also enables parallel assembly ofhigh-performance semiconductor devices (e.g., micro-LED displays) ontovirtually any substrate material, including glass, plastics, metals,other semiconductor materials, or other non-semiconductor materials. Thesubstrates can be flexible, thereby permitting the production offlexible electronic devices. Flexible substrates can be integrated intoa large number of configurations, including configurations not possiblewith brittle silicon-based electronic devices. Additionally, plasticsubstrates, for example, are mechanically rugged and can be used toprovide electronic devices that are less susceptible to damage orelectronic-performance degradation caused by mechanical stress. Thus,these materials can be used to fabricate electronic devices bycontinuous, high-speed, printing techniques capable of generatingelectronic devices over large substrate areas at low cost (e.g.,roll-to-roll manufacturing).

Moreover, these micro-transfer printing techniques can be used to printsemiconductor devices at temperatures compatible with assembly onplastic polymer substrates. In addition, semiconductor materials can beprinted onto large areas of substrates thereby enabling continuous,high-speed printing of complex integrated electrical circuits over largesubstrate areas. Moreover, flexible electronic devices with goodelectronic performance in flexed or deformed device orientations can beprovided to enable a wide range of flexible electronic devices.

The disclosed technology relates generally to the formation oftransferable micro inorganic light-emitting diode (e.g., micro-LED)devices. Micro-assembled micro-LED displays and lighting elements usearrays of micro-LEDs that are too small, numerous, or fragile toassemble by conventional means (e.g., vacuum grippers or pick-and-placetools). The disclosed technology enables micro-assembled micro-LEDdisplays and lighting elements using micro-transfer printing technology.The micro-LEDs can be prepared on a native substrate and printed to adestination substrate (e.g., plastic, metal, glass, or other materials)for example a display substrate. This enables a small active-areadisplay, as semiconductor material is only used for the micro-LEDs orother active elements (e.g., drivers or transistors) and not across theentire display panel or a substantial portion thereof as is commonlyfound in thin-film displays (e.g., in certain embodiments, the presentinvention, provides display substrates with an active area less than orequal to 40%, 30%, 20%, 10%, 5%, 3%, 1%, 0.5%, or 0.1% of the display).In certain embodiments, the combined light-emissive areas of the lightemitters is less than or equal to one eighth, one tenth, one twentieth,one fiftieth, one hundredth, one five-hundredth, one thousandth, onetwo-thousandth, or one ten-thousandth of the contiguousdisplay-substrate area.

Micro-assembled micro-LED displays and lighting elements can providesubstantially monochromatic, substantially white, or substantiallytunable color. They can include micro-LEDs that emit substantiallysimilar colors, for example, all blue or all red micro-LEDs, or they caninclude micro-LEDs of different colors, for example red, green, blue,yellow, or cyan micro-LEDs for rendering different colors on a displayor lighting element. The colors of the micro-LEDs can be produced bydirect emission from the micro-LEDs, by color conversion structures, orsome combination thereof.

Micro-LEDs used in the disclosed displays, in some embodiments, benefitfrom passivation of the active junction perimeter. For example, prior toprinting micro-LEDs to a display substrate, the junction perimeter ofeach micro-LED diode can be exposed (e.g., by etching) and a high bandgap semiconductor (e.g., InGaAlP, InGaN, GaN, AlGaN) can be grown on theexposed junction perimeter, thereby reducing non-radiative recombinationin the micro-LED.

Moreover, in certain embodiments, micro-LEDs carry current laterally asmaller distance than much larger, conventional LEDs. Accordingly, themicro-LED epi-structure can be thinner than the structures used forconventional LEDs. The micro-LED epi structure for displays can includethinner current-spreading layers or thinner buffer layers. In certainembodiments, conventional buffer layers can be omitted due to theepi-structure for micro-LEDs. Buffer layers are often needed as thethickness of a device increases to prevent the device substrate fromcracking. The disclosed technology provides for such devices (e.g.,devices less than a millimeter thick in some embodiments. Thin devicessuch as these do not need a buffer layer to prevent cracking of thesubstrate/device. In some embodiments, thin, strain-balanced alternatingepitaxial layers can be used in place of the conventional buffer layers.By using alternating layers of crystalline material with differentlattice structures, an overall structure with reduced strain is providedthat can also serve the overall function of the epitaxial layers, forexample for current conduction or light emission.

FIG. 1 is a prior-art illustration of a typical pixel 100 used, forexample, in an LCD display. The pixel 100 includes three subpixels 104a, 104 b, and 140 c (collectively 104). In some cases, these are redsubpixel 104 a, green sub pixel 104 b, and blue subpixel 104 c. A colorfilter is typically used to create the color for each subpixel 104 whilea backlight is used to illuminate the filters. The intensity of eachsubpixel 104 can be controlled through the variation of voltage appliedto each subpixel 104 such that a wide range of shades (e.g., 256 shades)are produced by each subpixel 104 (e.g., 256 shades of red, 256 sharesof green, and 256 shades of blue). In a liquid crystal display, thevoltage is applied to liquid crystals in a liquid-crystal layer. Theliquid crystals twist based on the voltage applied, thereby varying theamount of light from the backlight that passes through the liquidcrystals and thus through the color filters for each subpixel 104.

FIG. 2 is an illustration of an example pixel 200 constructed inaccordance with the disclosed technology. In this example, the pixel 200has a size similar to the size of the pixel 100 shown in FIG. 1,however, the pixel 200 shown in FIG. 2 is constructed using micro-LEDs202 a-202 f (collectively micro-LEDs 202). The micro-LEDs 202 can bemicro-transfer printed onto a substrate, such as a transparent(including semi-transparent, virtually transparent, and mostlytransparent) or flexible substrate. In some embodiments, the substrateis plastic, glass, metal, or sapphire.

Micro-assembled sparsely integrated high-performance light emitters suchas micro-LEDs 202 and a driver circuit 204 (e.g., a micro integratedcircuit) make bright displays that are flexible, draw less power, oroccupy only a small fraction of the display substrate. In someembodiments, the additional free space facilitates locatinghigher-functioning devices (e.g., micro-sensor 206) on the displayplane, such as devices that enable gesture sending, power harvesting,light-emitter redundancy, image capture, and wireless operation. Forexample, in some embodiments, a display includes a micro integrateddriver circuit 204 in each pixel. Additionally, the small operationalarea occupied by the micro-LEDs, in some embodiments, enables theconstruction of transparent displays, multi-mode displays, redundantmicro-LEDs and other devices, and super-bright displays.

FIG. 3 illustrates LEDs assembled using micro assembly (e.g.,micro-transfer printing) on display substrates. Small LEDs are placed ona display substrate and electrically connected in an active matrix, apassive matrix, in series, in parallel, or in some combination thereof.Micro-assembled LED displays and lighting elements exhibit manydesirable properties, including superior color quality in someembodiments. They are highly efficient and have low power consumption.

As shown in this example, micro-assembled LED displays can be producedto be transparent (e.g., having a transparency greater than or equal to50%, 80%, 90%, or 95% for visible light). Transparency can be based atleast in part on fractionally low area coverage or transparency ofmicro-LEDs, connection features, and other constituents. Thetransparency is apparent in the ‘off’ state of the device or when viewedfrom certain orientations (e.g., from the side of the device oppositethe viewing direction). The transparency can enable effectivelyinvisible displays or light sources. FIGS. 49A-49G illustrate an examplepartially transparent display constructed using a glass substrate. Insome embodiments, partial or virtual transparency is achieved withoutmicro-assembly techniques, provided that the pixel density issufficiently low and the intended proximity of an observer issufficiently far.

FIG. 4 is an illustration of an example of a micro-LED display 400 thatincludes redundant RGB inorganic micro-LEDs 402 a-402 x, a drivercircuit 406 (e.g., a micro-transfer printed integrated circuit), andmicro-sensors 404 a and 404 b (collectively micro-sensors 404). In someembodiments, the display 400 is formed on a display substrate that canbe polymer, plastic, resin, polyimide, polyethylene naphthalate,polyethylene terephthalate, metal, metal foil, glass, a semiconductor,or sapphire. The display 400 includes micro-transfer printed redundantRGB micro-LEDs 402 a-402 x that exhibit low power consumption whilestill projecting bright light. Each primary micro-LED (e.g., 402 a, 402c, 402 e, 402 g, 402 i, 402 k, 402 m, 402 o, 402 q, 402 s, 402 u, 402 w)includes a corresponding redundant, spare micro-LED (e.g., 402 b, 402 d,402 f, 402 h, 402 j, 4021, 402 n, 402 p, 402 r, 402 t, 402 v, 402 x,respectively). The sparsely integrated micro-LEDs 402 allow otherfunctional devices to be placed within each pixel, such as micro-sensors404 a and 404 b, power harvesting devices, gesture sensors, orimage-capture devices.

Micro integrated driver circuits 406 (e.g., CMOS circuits) can bemicro-transfer printed to drive the micro-LEDs 402. The micro integrateddriver circuits 406 can include embedded memory (e.g., non-volatilememory). Memory can be used to display static images without constantlyneeding to refresh the display (e.g., thereby saving power). The memorycan also store a lookup table(s) used, for example, to adjust the outputof micro-LEDs in the display. In some embodiments, each pixel has amicro integrated driver circuit 406 located thereon to drive eachmicro-LED in the respective pixel.

In addition to emitting light from the front of the display 400, themicro-LEDs 402 a-402 x can also emit light from the back of the display400. The display 400 can include an adhesive layer on one side,producing a decal-like display. The wiring used in the display, such asthe wiring used to electronically couple the micro-LEDs 402 andmicro-sensors 404 to the integrated driver circuit 406, can be finewires (e.g., with critical dimensions less than 1 μm and an overlayaccuracy of less than 0.25 μm) or transparent wires.

FIG. 7 is an illustration of a micro-assembled display 700 that includesprimary and redundant RGB inorganic micro-LEDs 702 a-702 x (collectivelymicro-LEDs 702) arranged in pairs of primary and redundant inorganicmicro-LEDs, a driver IC 706, and micro-sensors 704 a and 704 b(collectively micro-sensors 704) on a substrate. The substrate can betransparent or flexible. A lookup table can be used to electronicallyproduce a visually perfect display by providing extra light from onemicro-LED of a redundant pair (e.g., micro-LEDs 702 a and 702 b) in theevent that its mate is non-functional. For example, if micro-LED 702 ais non-functional, the driver 706 can cause micro-LED 702 b to beactivated to compensate for micro-LED 702 a. In another example, if allof the micro-LEDs are being driven to provide a high-resolution display,micro-LED 702 b can be driven to provide extra light (e.g., brighter) tocompensate for micro-LED 702 a if micro-LED 702 a is non-functional.

FIG. 5 is an illustration of an example pixel 500 in accordance with thedisclosed technology. As explained above, small micro-LEDs 502 allow forredundancy (e.g., the LEDs with at least one of a width, length, andheight from 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, 20 to 50 μm, 50 to 100μm, or 100 to 250 μm Redundancy can produce a visually perfect displayand account for malfunctioning micro-LEDs (e.g., displays produced withelectrically shorted or open micro-LEDs). In some embodiments, if onemicro-LED is defective or missing, this will be corrected by theexternal drive electronics. For example, each micro-LED (e.g., 502 a,502 c, and 502 e) can have a corresponding spare or redundant micro-LED(e.g., 502 b, 502 d, 502 f, respectively), thereby providing twointerlaced displays—a primary display and a secondary display that canbe activated on an individual micro-LED basis. In some embodiments, boththe primary and secondary micro-LEDs are wired to the display orintegrated circuits. In some embodiments, the redundant micro-LEDs arewired on an individual basis after testing the display. In this example,the red primary micro-LED 502 a has a corresponding redundant redmicro-LED 502 b, the blue LED 502 c has a corresponding redundant bluemicro-LED 502 d, and the green LED 502 e has a corresponding redundantgreen micro-LED 502 f.

Each micro-LED can have its own pixel driver (e.g., transistor circuit).This can be used to form high-resolution displays. The micro-LEDs can bechosen to operate in many different modes, such as a normal operationmode or a high-resolution mode. This provides a tunable resolution(e.g., more light emitters can be activated to provide a higherresolution display as needed) that can be set automatically (e.g., basedon the material being viewed on the display) or by a user.

In some embodiments, the display has a tunable brightness dynamic range.If more emitters are turned on, the display will be brighter. This isuseful for a variety of applications, including improving daylightreadability or in bright ambient environments. The display can also beused to form a color-tunable flash by activating a mix of micro-LEDs(e.g., to provide a warm light glow). Alternatively, the micro-LEDs canbe provided in a dense pattern to increase the intensity of the flash.

Redundant pairs of micro-LEDs can be connected physically in series orparallel, before or after a repair operation. Physical repair caninclude laser cutting of unwanted electrical traces, direct writing ofelectrical traces by chemical vapor deposition or laser-assistedchemical vapor deposition or inkjet printing. Redundant pairs ofmicro-LEDs can be electrically independent and operate independently.Displays can also employ redundant drive circuitry and display controlelements for improved information display fidelity or to facilitate theproduction of visually perfect displays.

FIG. 6 is an illustration of an example multi-color pixel 600 of adisplay with a missing micro-LED 604. In this example, the pixel 600 isdesigned to include a primary set of RGB micro-LEDs—red micro-LED 602 a,green micro-LED 604, and blue micro-LED 602 d—and a spare set of RGBmicro-LEDs—red micro-LED 602 b, green micro-LED 602 c, and bluemicro-LED 602 e. However, in this case, the primary green micro-LED 604is missing or non-operational while the primary blue 602 d and red 602 amicro-LEDs are present and operational. The primary green micro-LED 604may have been unintentionally omitted (e.g., because of a printingerror), it may have been removed after printing because it was adefective micro-LED, or it can be present but non-functional (e.g.,open). The spare green micro-LED 602 c can supplement the omittedprimary green micro-LED 604. The spare red and blue micro-LEDs can beturned off as the primary red and blue micro-LEDs 602 a, 602 d areoperational. In some embodiments, electronic circuits sense missing ordefective micro-LEDs and activate the corresponding spare micro-LED. Thedriving circuits for the display can sense defective micro-LEDs. In someembodiments, the defective micro-LEDs are sensed by a detection circuitthat is separate from the display. Defective micro-LEDs can be removedor disconnected. In some embodiments, replacement micro-LEDs areconnected to replace the defective micro-LEDs. In some embodiments, thereplacement micro-LEDs are already connected and the defectivemicro-LEDs must just be removed or disconnected if necessary. In someembodiments, both the primary and redundant micro-LEDs are connected tothe display circuit and the driving circuit(s) merely drives theappropriate redundant spare micro-LEDs if a primary micro-LED isdefective.

FIGS. 8A through 8D illustrate redundancy of micro-LEDs in a micro-LEDpanel for micro-assembled displays and lighting elements. FIGS. 8Athrough 8C are enlarged illustrations of the identified regions of thedevice shown in FIG. 8D. Redundant micro-LEDs in a micro-assembledmicro-LED panel provide defect tolerance and facilitate the formation ofvisually perfect displays and lighting elements. During a firstconnection step, as illustrated in FIG. 8A, some fraction of themicro-LEDs (e.g., micro-LED 802) are connected to form circuits, whereasthe remaining micro-LEDs (e.g., micro-LED 804) are left disconnectedfrom the circuit and form redundant micro-LEDs (e.g., back up, spare, orreplacement micro-LEDs that can be used to compensate for or replacedefective primary micro-LEDs). In some embodiments, when the connectionto micro-LED 802 is formed, electrically conductive contact features 806a and 806 b are formed to the redundant device 804 even though theredundant device 804 is not connected to the greater circuit thatincludes the micro-LEDs 802. Testing procedures can be used to identifydefective micro-LEDs or groups of micro-LEDs that are unintentionallydisconnected from the circuit (e.g., “open”) or unintentionally shorted.As shown in FIG. 8B, by directly and physically writing electricaltraces, redundant micro-LEDs (e.g., micro-LED 810) that are in closeproximity to defective non-redundant micro-LEDs (e.g., micro-LED 808)are connected to the circuit. In some embodiments, electrically shortednon-redundant micro-LEDs (e.g., micro-LED 812) are similarlydisconnected from the circuit as shown in FIG. 8C using, for example,ablation. In some embodiments, the defective, non-redundant LED (e.g.,812) is not disconnected after connecting the corresponding redundantLED to the display circuit.

FIGS. 9A through 9C are images that illustrate a micro-transfer printedarray of micro-LEDs on a display substrate, such as glass. Each pixel902 includes a primary micro-LED 906 and a spare micro-LED 904 that canbe connected after testing the display. Upon identification of an openpixel, for example, because of a missing or defective micro-LED, thespare micro-LED can be connected as shown in FIG. 9B (e.g., pixel 908has a faulty primary micro-LED and a connected redundant micro-LED andpixel 910 has a missing primary micro-LED and a connected redundantmicro-LED) and FIG. 9C. In this example, ink jet printing of colloidalsilver particles serves as a direct write method to connect the sparemicro-LEDs, as shown in FIG. 9B. In some embodiments, unused redundantmicro-LEDs are removed from the display. In some embodiments, thedefective primary micro-LEDs are removed or disconnected (e.g., beforeor after connecting a corresponding redundant micro-LED). In someembodiments, defective primary micro-LEDs are disconnected or removed ifthe defect is such that the micro-LED is shorted (e.g., if the defect issuch that the defective primary micro-LED is open it may not benecessary to remove that micro-LED). In the example shown in FIG. 9C,the display includes 48 pixels, each including a primary micro-LED and aredundant micro-LED as shown in FIG. 9A. Pixels 912 a-912 f each includea defective primary micro-LED and thus a redundant micro-LED has beenelectrically connected to the display circuit to compensate/replace eachof these defective primary micro-LEDs.

FIG. 10 is an illustration of an example method for repairing micro-LEDarray devices using micro-assembled jumpers to electrically connect aredundant micro-LED 1004 b because a primary micro-LED 1006 b isdefective. A conductive jumper element 1002 can be placed by microassembly (e.g., micro-transfer printing) for repairing a micro-LED arraydevice by establishing an electrical connection to a spare, redundantmicro-LED 1004 b. In some embodiments, a conductive structure isprepared for micro assembly and assembled, thereby electricallyconnecting a redundant micro-LED 1004 to the display circuit. Aconnection between traces on the micro-LED array device is establishedthereby connecting a redundant micro-LED 1004 b to the rest of theconnected array. Electrical connection can be established by solderreflow, or contact between clean metal surfaces using, for example, ajumper 1002 (e.g., gold-gold interfaces).

As shown in this example, a jumper 1002 is used to connect redundantmicro-LED 1004 b to effectively replace defective primary micro-LED 1006b. Redundant micro-LED 1004 a is not connected in this example becauseprimary micro-LED 1006 a is functioning properly. In some embodiments,redundant micro-LED 1004 a is connected at a later time if primarymicro-LED 1006 a fails. In some embodiments, unused redundant micro-LEDs(e.g, micro-LED 1004 a) are removed from the display. In someembodiments, the defective primary micro-LEDs (e.g., micro-LED 1006 b)are removed (e.g., before or after connecting a corresponding redundantmicro-LED). In some embodiments, defective primary micro-LEDs (e.g.,1006 b or primary micro-LEDs discussed in other embodiments) are removedif the defect is such that the micro-LED is shorted (e.g., if the defectis such that the defective primary micro-LED is open it may not benecessary to remove that micro-LED).

Non-functional micro-LEDs can be sensed in a number of ways. Forexample, a camera can be used to detect light emitted from one or moremicro-LEDs. The camera can be specific to a certain color spectrum. Insome embodiments, the camera is a light sensor incorporated into thedisplay panel (e.g., a micro-sensor micro-assembled in or on the sameplane or surface as the micro-LEDs). The micro light sensor, in someembodiments, is connected to the micro integrated circuit (e.g., thatforms the display driver for a pixel or the display). The light sensorsignal, in some embodiments, is interpreted by the micro integratedcircuit. The micro integrated circuit can drive a secondary micro-LED inthe situation in which a primary micro-LED is nonfunctional. In someembodiments, the micro integrated circuit will not drive thedefective/non-functional micro-LEDs. The micro integrated circuit canalso alter how it drives a primary micro-LED in certain situations toensure that the appropriate color is output by the micro-LED (e.g., thecorrect shade of red). In some embodiments, the display can perform thisanalysis and correction after it is manufactured and used by a consumer.This can increase the lifespan and quality of displays.

FIGS. 11A and 11B illustrate micro-assembled cross-overs 1102, 1104, and1106, for layer reduction in micro-LED array devices. Reducing thenumber of process steps to be performed on the micro-LED device is oftenadvantageous. Additionally, some micro-LED devices, such as thoseutilizing active- or passive-matrix architectures, benefit from orrequire cross-over of data or power lines and traces. A typical way toaccomplish this kind of cross-over is to pattern a dielectric layer withelectrically conductive vias between two metal layers to electricallyconnect the two metal layers. However, this increases the cost ofmicro-LED devices by adding additional steps to the processing of thedisplay substrate.

Providing electrical cross-over by micro assembly (e.g., cross-overs1104 and 1106) provides a way to eliminate the large-area processingsteps of providing the dielectric layer and the second metal layer,thereby reducing costs by supplying the cross-over in an area-denseconfiguration on a native substrate and micro assembling the cross-overon the device substrate in a less-dense configuration. Micro-LED devicesthat use cross-overs assembled in this way (e.g., cross-overs 1102,1104, and 1106) can also benefit from redundancy for defect tolerance inthe micro-LED array device by providing redundant wires and a method forforming electrical connections across defective, open wires.

This type of layer reduction can be accomplished by a simple passivedevice 1102, such as a conductive jumper as described in relation toFIG. 13 below, or an integrated device 1104 that include cross-oversand, for example, other functionalities such as CMOS drive circuitryand/or non-volatile memory housed within a structure suitable for microassembly. In some embodiments, the structure suitable for micro assemblyincludes more than one cross-over, each cross-over having electricalinsulation between it and at least one other cross-over housed in thestructure suitable for micro assembly.

FIGS. 12A and 12B are illustrations of example systems that use aresistor 1206 or diode 1208, respectively, to facilitate repair byproviding information in the form of the electrical signature of aredundant micro-assembled micro-LED pixel or sub-pixel in a lightingelement or display. In some embodiments, pixels or sub pixels areprovided with a spare micro-LED 1204 wired by default in parallel witheach primary micro-LED 1202 of a pixel or sub pixel. For example, arepair for this embodiment can consist of severing connections toshorted micro-LEDs without providing additional directly written metalfeatures to connect the spares. In some embodiments, each pixel or subpixel that includes a spare micro-LED 1204 wired by default in parallelwith a primary micro-LED 1202 also includes a resistor 1206 or diode1208 in series with the spare micro-LED 1204, as shown in FIGS. 12A and12B, respectfully.

As shown in FIG. 12A, in some embodiments, a resistor 1206 is placed inseries with a spare micro-LED 1204. In this example, a severely shortedprimary micro-LED 1202 will exhibit an electrical signature (acurrent-voltage relationship) that shows a resistance less than theresistor 1206 in series with the spare micro-LED 1204. A severelyshorted spare micro-LED 1204 will show a resistance not less than theresistor in series, thereby providing an electrical signature thatinforms the repair process of which micro-LED, the primary 1202 or spare1204, needs to be disconnected from the array in order to form avisually perfect micro-assembled micro-LED display or lighting element.As illustrated in FIG. 12B, a diode 1208 in series with the sparemicro-LED 1204 will inform which micro-LED needs repair in a shortedsub-pixel based on turn-on voltage signatures.

FIG. 13 illustrates cross-sectional views of five different types ofelectrical connectors 1302, 1304, 1306, 1308, 1310 or “jumpers” suitablefor micro assembly. In some embodiments, the electrical connectorsinclude exposed noble metal surfaces, including gold, silver, orplatinum. In some embodiments, the electrical connectors include exposedmetal surfaces including copper, stainless steel, aluminum, titanium,nickel, or chromium. In some embodiments, the electrical connectorsinclude solders, like PbSn, AgSn, AgSn, or alloys thereof, or othersolder alloys.

In some embodiments, the connectors (such as 1302) are formed on anative substrate, such as silicon, SOI, GaAs, polymer, or glass, andreleased from the native substrate by etching a sacrificial layer. Theconnectors can be transferred to an intermediate stamp or substrate inorder to invert them. The connectors can include metals only (e.g.,connector 1310).

In some embodiments, the connectors must “jump” or pass over wires toconnect to points. For example, a jumper can be used to connect pad 3802to pad 3804 as shown in FIG. 38, however, the jumper must notconductively contact the wires passing between these pads. In thesecases, various designs can be used to ensure that the appropriate wiresare passed (“jumped”) over and not shorted. For example, connectors 1304and 1306 include metals and dielectrics. The dielectric material canpass over the wires that are not intended to be connected by theconnector, thereby ensuring these wires are not shorted to the connectoror the pads 3802 and 3804. Referring back to FIG. 13, a portion of theconnector can be recessed such that the wires between two jumper padsare not contacted as shown by connectors 1304, 1308, and 1310.Similarly, as illustrated by connector 1308, an insulator can be used toprevent the jumper from conductively contacting the wires passingbetween two pads (e.g., pads 3802 and 3804 as shown in FIG. 38).

Additionally, the connectors can include a combination of more than oneof metals, polymers, inorganic dielectrics, semiconductors andsemi-insulating semiconductors. The connector can have an electricallyinsulating exposed surface positioned between two exposed electricallyconductive regions of a surface.

FIG. 14 is an illustration of a micro-assembled display 1400 thatincludes primary RGB inorganic micro-LEDs (e.g., micro-LEDs 1402 g, 1402k, 1402 m, 1402 o, 1402 u, and 1402 w) and supplementary RGB inorganicmicro-LEDs (e.g., micro-LEDs 1402 b, 1402 d, 1402 f, 1402 h, 1402 j, 402n, 1402 p, 1402 r, 1402 t, 1402 v, and 1402 x). In some embodiments,some but not all of the pixels in this display include multiple R, G, orB micro-LEDs to augment the brightness of the display for extra-brightflashes of light or camera flashes or daylight viewability. For example,micro-LEDs 1402 a, 1402 c, 1402 e, 1402 i, 14021, 1402 o, 1402 q, and1402 s are indicated but omitted in the example shown in FIG. 14. Theseomitted micro-LEDs can be intentionally or unintentionally omitted. Forexample, they may not have been printed or they may have been removedbecause they were defective.

Some of the supplementary micro-LEDs can be different shapes, sizes(e.g., micro-LED 1402 u), or colors than the other micro-LEDs in thedisplay. A lookup table can be used to facilitate image and lightingquality optimization for all conditions. In some embodiments, thedisplay includes a micro integrated circuit 1406 and micro-sensors 1404as described above. For example, each pixel can include a microintegrated circuit 1406 and one or more micro-sensors 1404.

FIGS. 15A and 15B are illustrations of micro-assembled micro-LED displayand lighting element architectures. In some embodiments, the display,such as the display shown in FIG. 15A, facilitates repair withoutbuilt-in redundancy by providing space and circuitry on the substratefor supplementary micro-LEDs. A micro-assembled micro-LED displayarchitecture that can incorporate spare micro-LEDs 1502 after connectionof an array of primary micro-LEDs 1504 provides a way to producevisually perfect micro-assembled micro-LEDs, without requiring asupplementary micro-LED at each sub pixel as in a fully redundantarchitecture. A supplementary micro-LED (e.g., shown in dashed lines inFIG. 15A) is provided (e.g., by micro-transfer printing) only ininstances in which a primary micro-LED is defective. The supplementarymicro-LEDs can be printed to locations 1502 a-1502 d as necessary. Insome embodiments, the connections to locations 1502 a-d are alreadyformed such that the supplementary micro-LEDs are electrically connectedto the display circuit upon printing.

As shown in FIG. 15B, in some embodiments, the display or lightingelement architecture including a light emitter such as a micro-LED 1516and metal interconnection features 1506 a and 1506 b (collectively 1506)embedded in or placed on a tacky or conformable layer 1508 on a displaysubstrate 1512 to which the micro-LEDs are micro-transfer printed, sothat the metal interconnection features 1506 are exposed on at least onesurface of the tacky 1508 or conformable layer and can be connected tothe light emitter 1516.

A device can include an array of micro-assembled micro-LEDs. Eachmicro-LED has two contacts on one side—the same side that contacts thetacky or conformable layer 1508 so that the contacts of the micro-LEDsmake contact with the metal interconnection features 1506. The spacingof the metal interconnection features 1506 a and 1506 b, and tacky layer1508, as well as the design of the micro-LEDs 1516 is such that thereare increased tolerances for placement of each micro-LED 1516, therebyincreasing production yield. A portion 1514 of the tacky layer contactsthe underside of the micro-LED 1516 thereby securing the micro-LED inplace once it is micro-transfer printed to the display substrate 1512.

Micro-LEDs can be tested immediately after assembly, and additionalmicro-LEDs can be assembled after testing for repair. The architecturecan include redundant interconnection features at each sub pixel toaccept additional micro-LEDs for repair. The architecture can include areflective layer 1510 positioned underneath at least a portion of thetacky layer. The reflective layer 1510 can be metallic and can beelectrically conductive or used as an electrical conductor.

FIG. 16 illustrates a micro-assembled micro-LED on a non-native displaysubstrate 1604 separate and distinct from a native source substrate onor in which the micro-LEDs are formed. In some embodiments, thearchitecture of the lighting element as shown in FIG. 16 facilitatesrepair without built-in redundancy. An array of micro-LEDs for microassembly can be provided with the micro-LEDs having two terminals 1602 aand 1602 b (collectively 1602) facing downward, opposite a contactsurface of the micro-LEDs that is to be contacted by a transfer element.The micro-LEDs can have one or more electrically conductive protrusionsextending downward from each terminal Additionally, the protrusions canextend beyond other features on the micro-LEDs. The protrusions(terminals 1602 a and 1602 b) can contact and penetrate a portion of themetal interconnection features (contact pads) 1608 a and 1608 b(collectively 1608) to increase electrical connectivity after printing.

A display substrate 1604 can be provided optionally with reflectivelayers or patterns as shown in FIG. 15B. In some embodiments, thedisplay substrate 1604 includes a tacky or compliant layer 1606 (e.g.,PDMS) and metal interconnection features 1608 (e.g., metalinterconnection features with a gold, platinum, tin, copper, or silversurface).

In some embodiments, the tacky layer 1606 is deposited on the displaysubstrate 1604, and the metal interconnection features 1608 deposited ontop of the tacky layer 1606 (e.g., by physical deposition, transfer,micro assembly, transfer printing, and/or patterning). The array ofmicro-LEDs can be assembled onto the display substrate 1604 via atransfer element. The micro-LEDs can be adhered to the tacky layer 1606,establishing electrical connectivity from the contacts 1602 of themicro-LEDs to the metal interconnection structures 1608. In someembodiments, the micro-LEDs are adhered to the metallic interconnectionlayers 1608. In some embodiments, the formation (e.g., size) of theterminals 1602 is such that it provides increase tolerance for placementof each micro-LED on the display. As shown in FIG. 16, the micro-LEDcould be placed further to the left or right of the non-native substrate1604 and the terminals 1602 would still contact their respectiveinterconnection features 1608.

After depositing the micro-LEDs on the display substrate 1604, themicro-LEDs can be tested, micro-LEDs can be added as desired (e.g., toreplace or substitute for defective micro-LEDs), and metalinterconnection features 1608 can be severed as desired (e.g., todisconnect defective micro-LEDs). This process can be repeated asdesired. These techniques can be used to produce visually perfectmicro-LED displays and lighting elements.

FIG. 17 is an illustration of an example display 1700 formed by twoindependent displays occupying the same viewable area 1702. One displaycan compensate for defects in the other. Independent, coordinated driverchips can control each display. For example, each independent displaycan have its own row driver and column driver. As shown in FIG. 17, afirst display is driven by column driver 1704 and row driver 1706 whilethe second display is driven by column driver 1708 and row driver 1710.

The pixels of independent displays can occupy the same plane or belocated on the same surface of the display or they can be spaced apart,for example separated by a distance (e.g., Controlled by placing adielectric layer between each independent display). FIG. 18 is anillustration of a stacked micro-LED display 1800. Transparent micro-LEDdisplays 1802 a-1802 d (each of which can be a display such as display400 as described in relation to FIG. 4) can be stacked in a verticaldimension. This allows for tunable brightness and can also compensatefor defects. For example, instead of locating spare micro-LEDs on thesame surface or in the same plane as primary micro-LEDs, the sparemicro-LEDs can be located on a separate surface, thereby forming astacked display from several independent, fully-functional displays.Additionally, stacked transparent micro-LED displays can be used to form3-D displays.

FIG. 19 is an illustration of a micro-assembled stacked display 1900formed of three display panels 1902 a-1902 c (each of which can be adisplay such as display 400 as described in relation to FIG. 4).Different numbers of display panels can be used to provide variouseffects and increased definition. In this example, the micro-assembleddisplay includes redundant RGB inorganic micro-LEDs, driver ICs,sensors, and transparent substrates. The display uses multiple levels ofdisplay panels for defect tolerance, increased brightness,2.5-dimensional or 3-dimensional information display, or increasedresolution.

Display panels with different resolutions, such as display panels 2002 aand 2002 b, can be used to form a stacked display 2000 as shown in FIG.20. The displays in the stack can also be different sizes. Themicro-LEDs can also be different sizes, colors, or in differentlocations. The display 2000 shown in FIG. 20 includes two same-sizeddisplay panels 2002 a-2002 b. The micro-LEDs on the first display panel2002 a are smaller than the micro-LEDs on the second display panel 2002b. Additionally, the micro-LEDs on the first display panel 2002 a are ina different location than the micro-LEDs on the second display panel2002 b. In this example, the display panels 2002 a and 2002 b have adifferent resolution. Display panel 2002 a includes 24 micro-LEDs (e.g.,micro-LEDs 2004 a-2004 x) and display panel 2002 b includes only 6micro-LEDs (e.g., micro-LEDs 2006 a-2006 f). Each display panel 2002 aand 2002 b, in some embodiments, includes a driver (e.g., microintegrated circuit) 2010 a and 2010 b, respectively. In someembodiments, a single driver is used for each display panel (e.g., 2002a and 2002 b) in a stacked display.

Micro-LED emitters, in some embodiments, are used to form multi-modedisplays. FIG. 21 is an illustration of an example pixel 2100 of amulti-mode display. An emissive micro-LED display 2102 can be combinedwith a second type of display 2104, such as a reflective display,electrophoretic, or MEMs-based display to form a multi-mode display. Inthe example shown in FIG. 21, the second display 2104 is a reflectivedisplay. The micro-LEDs 2106 a-2106 f will only utilize a fraction ofthe pixel area while the reflective component 2104, for example, canutilize some of the area of pixel 2100 as well. For example, a mobiledevice, such as a cell phone (including smart phones) or a tabletcomputing device can switch between the display type, thereby allowingthe micro-LED display 2102 to be used while watching a video or viewingpictures, for example, while an ultra-low power “paper-like” display(e.g., electrophoretic display) or reflective display (such asreflective display 2104) can be used for reading.

In some embodiments, as shown by the pixel 2200 illustrated in FIG. 22,micro-LEDs 2204 a-2204 f can be placed on top of a reflective element2202 without greatly interfering the reflective display element giventhe small size of the micro-LEDs 2204 a-2204 f.

As discussed previously, displays (e.g., micro-LED displays) can beinterlaced with micro-transfer printed sensors and transceivers. FIG. 23is an illustration of a pixel 2300 with an integrated circuit 2306connected to the micro-LEDs 2302 a-2302 f (e.g., micro-LEDs 2302 a-2302b form a redundant pair, micro-LEDs 2302 c-2302 d form a redundant pair,and micro-LEDs 2302 e-2302 f form a redundant pair) and a micro-sensor2304. For example, the display can be interlaced with image capturedevices (e.g., optical sensors, photodiodes), infrared sensors (e.g.,gesture sense or IR camera), temperature sensors (e.g., feedbackregarding micro-LEDs to provide color/brightness correction), andwireless transmission devices. The display can also include powerharvesting devices such as solar cells (collection of light),motion-energy scavenging (e.g., piezoelectric devices), capacitors tostore energy, or antennas for harvesting electromagnetic radiation. Thetransfer printed elements interlaced with the display can be printed atdifferent densities (sparseness) according to the desired function andapplication. For example, fewer temperature sensors are necessary, buteach pixel may require an image capture device.

FIG. 24 is an example illustration of the color gamut of human visionand an HDTV. The disclosed technology can be used to improve the colorgamut of a display to more closely match the color gamut of humanvision.

As illustrated in FIG. 25, micro-LED displays can include variouscolored micro-LEDs to, among other things, improve the color gamut ofdisplays. In addition to the standard red micro-LEDs 2502 a-2502 b, bluemicro-LEDs 2502 e-2502 f, and green micro-LEDs 2502 g-2502 h, micro-LEDdisplays, in some embodiments, include yellow micro-LEDs 2502 c and 2502d, for example as in the pixel 2500 shown in FIG. 25, or other colormicro-LEDs (e.g., cyan). In another example, the pixel 2500 can includetwo different red, green, or blue micro-LEDs (e.g., green micro-LED 2502c emits a different shade of green light than 2502 d). This allows foran improved color gamut (e.g., more achievable colors). The display mayalso include a micro integrated circuit 2506, micro-sensor 2504, orother semiconductor elements as described above.

FIG. 26 is an illustration of an example pixel 2600 for use in amicro-assembled inorganic micro-LED array for yielding visually perfectdevices. The pixel 2600 includes six sub pixels 2608 a-2608 f, eachhaving a different color (e.g., One sub-pixel 2608 a having a red colormicro-LED 2602 a, another sub-pixel 2608 b having a different red colormicro-LED 2802 b, one sub-pixel pixel 2608 c having a green colormicro-LED 2602 c, another sub-pixel 2608 d having a different greencolor micro-LED 2602 d, one sub-pixel 2608 e having a blue colormicro-LED 2602 e and one sub-pixel 2608 f having a different blue colormicro-LED 26020. For example, the pixel 2600 can include six subpixels2608 a-2608 f, each having a micro-LED with a respective peak of outputintensity at 450, 460, 530, 540, 650, and 660 nm. A lookup table can beused to compensate for pixel non-uniformities.

FIGS. 27A-B are illustrations of two micro-assembled inorganic micro-LEDarray strategies for yielding visually perfect devices. The display 2700shown in FIG. 27A uses two micro-LEDs (2702 a and 2702 b) per sub pixel2704. The display 2750 shown in FIG. 27B utilizes more pixels (e.g.,2756 a-2756 d) per unit of area and less subpixels and/or micro-LEDs perpixel. In the example shown in FIG. 27B, there is only one micro-LED2752 per sub pixel 2754, however, there are two or more pixels (in thisexample, 4 pixels; 12 sub pixels) for each visually discernable regionof the display. In the event that one micro-LED is missing in display,adjacent pixels compensate using information from a lookup table. Forexample, if micro-LED 2752 a is missing, micro-LED 2752 b can be used tocompensate for the missing micro-LED.

FIG. 28 is an illustration of an example pixel 2800 prior to connection.In some embodiments, an array of micro-assembled micro-LEDs 2802 a-2802f can be illuminated and the photoluminescence can be observed toidentify defective micro-LEDs (e.g., 2802 a and 2802 e) prior toconnection. This can be used to trigger a physical repair, adding anextra micro-LED to a sub pixel that includes a defective micro-LEDidentified by photoluminescence testing. In this example, micro-LEDs2802 a and 2802 e were defective and removed. In some embodiments, as aresult, only micro-LEDs 2802 b, 2802 c, and 2802 f will be wired. Inother embodiments, 2802 d will also be wired. FIG. 28 also illustratesthe scenario in which micro-LED 2802 d is defective and an additionalmicro-LED 2802 c was printed to compensate for this defective micro-LED2802 d.

FIG. 29 is an illustration of implementing color conversion inmicro-assembled micro-LED displays and lighting elements using chips ofcolor-conversion material, for example a polyhedron such as a cube.Displays and lighting elements in some embodiments require full RGBcapabilities and/or colors that are different than the direct-emissionwavelength of their constituent micro-LEDs.

One method for accomplishing this color conversion is by using microassembly techniques to place an array of micro-LEDs 2904 a and 2904 bover, on, or in contact with corresponding arrays of color-conversionmaterial, for example, by forming recesses 2902 a-2902 h in a displaysubstrate 2906 that is at least partially transparent and filling therecesses with phosphors or other color-conversion materials.Color-conversion materials include phosphor-bearing gels or resins,phosphor ceramics, and single-crystal phosphors. Other color-conversionmaterials include direct band gap semiconductors, such as those that areparts of epitaxial stacks that in some embodiments include quantum wellsand surface passivation.

In an alternative color conversion approach, chips of color-conversionmaterial, for example, of a direct band gap semiconductor, aremicro-assembled on a display substrate, and at least a portion of amicro-LED array is assembled over the chips.

In some embodiments, devices are designed such that most or all of thelight emitted from the micro-LEDs emits downward, through a transparentdisplay substrate and optionally through a color-conversion material.This attribute imparts valuable characteristics to the devices that haveit, for example, as in a display or lighting element that is virtuallytransparent from one direction and a bright source of light orinformation display from the opposing direction. This attribute can beachieved by the formation of reflective structures entirely or almostentirely covering one side of the micro-LEDs (e.g., The “top” side ofthe micro-LEDs) with the micro-LED contacts, the array connectionmetals, and/or supplementary mirror structures formed on the displaysubstrate.

In an alternative approach to color conversion, the color conversionlayers are formed on top of or at least partially surrounding themicro-LEDs on more than one side of the micro-LEDs.

FIGS. 30A and 30B is an image and illustration of devices usingself-aligned dielectrics for micro-assembled micro-LED displays andlighting elements. In some embodiments, it is advantageous to reduce thenumber of alignment steps on the display substrate of a micro-assembledmicro-LED display or lighting element.

In some embodiments, micro-LEDs that include some materials that aresubstantially transparent to a specific wavelength are assembled on adisplay substrate that is also transparent to the same specificwavelength. The micro-LEDs have one or two metal contacts on the side ofthe micro-LED positioned opposite the interface between the micro-LEDand the display substrate. The micro-LEDs optionally also includedielectric materials (e.g., silicon oxide or silicon nitride) covering aportion of the side of the micro-LEDs opposite the display substrate.Prior to forming connections to the micro-LEDs, in some embodiments, itis beneficial to provide an insulating layer surrounding the perimeterof the micro-LED, thereby avoiding unwanted electrical shorting. Theinsulating layer is formed by depositing a layer of photo-definabledielectric (e.g., BCB, polyimide, PBO, epoxy, or silicone), exposing thephotoactive dielectric to light, shining the light from beneath thedisplay substrate, and cross-linking the photo-definable material exceptin the regions above the two metal contacts, thereby electricallyinsulating the perimeter of the micro-LEDs prior to the formation ofconnections.

In some embodiments, cameras with spectral responses that match humanvision can be used to define a lookup table for use with micro-assembledmicro-LED displays. Displays that use micro-assembled micro-LEDs benefitfrom uniformity in pixel-to-pixel brightness and color consistency. Theepitaxial and micro-fabrication processes that produce micro-LEDstypically produce micro-LEDs with a range of brightness and a range ofoutput spectrum. Displays that use assemblies of micro-LEDs, in someembodiments, benefit from a lookup table that characterizes the outputof each sub-pixel (e.g., allowing the display to drive each individualsub-pixel according to the relationship between brightness and currentfor that sub-pixel), thereby providing the information required toaccurately render images and colors as if the micro-LEDs of the devicesdid not have non-uniformity of color and brightness. Furthermore, thelookup table can account for the relationship between brightness, color,and efficacy in the human visual response.

In some embodiments, a camera and optical filter with a spectralresponse that matches the spectral response of the human eye are used toproduce a lookup table for a micro-LED display. In some embodiments, acamera and optical filter with a spectral response that matches thespectral response of the human visual blue response, a camera andoptical filter with a spectral response that matches the spectralresponse of the human visual green response, and a camera and opticalfilter with a spectral response that matches the spectral response ofthe human visual red response are used to produce a lookup table for amicro-LED display.

In some embodiments, arrays of micro-scale functional elements areinterlaced with arrays of micro-scale control elements. In someembodiments, arrays of assembled inorganic micro-scale functionaldevices are integrated with an interlaced array of assembled micro-scalecontrol elements. The control elements can include micro-scale siliconintegrated circuit devices that are integrated and interlaced with themicro-scale devices through micro-assembly methods. The micro-assemblymethod in some embodiments, is transfer-printing with an elastomerstamp, an electrostatic head, and/or vacuum-collet-based assembly tools.

The assembled micro-scale functional elements can be microlight-emitting devices such as light-emitting diodes (LEDs), verticalcavity surface emitting lasers (VCSELs) or edge-emitting lasers. Theassembled micro-scale functional elements can be sensing devices such asphotodiodes, radiation sensors, temperature sensors, and motion sensors.The assembled micro-scale functional elements can be energy harvestingor energy converting devices. The assembled micro-scale functionalelements can be actuator devices.

A single micro scale control element can control a cluster or array offunctional elements. In some embodiments, the control element isconnected with the cluster of functional elements through a network ofwires which fan-out from the control element to each functional element.The wiring, in some embodiments, is made of a deposited thin-film metal(e.g., Al, Cu, Mo, or Au) that is patterned.

The micro-scale control integrated circuit can include variousfunctionalities. The control elements can include memory, both digitaland analog circuits, sensors, signal processing circuits, and/or opticaltransceivers (e.g., providing optical I/O to and from the controlelement). The cluster of functional elements with a single controlelement can be operated as an independent unit within a larger array ofclusters. Each cluster of functional elements can be operated as anindependent display.

FIG. 31 is an illustration of an example 4×4 array 3100 of functionalelements 3102 a-3102 p (collectively 3102) controlled by a singlemicro-assembled integrated circuit 3104. The functional elements 3102can be connected with the control element 3104 through a singlethin-film metallization process. In some embodiments, the controlelement 3104 and functional elements 3102 are located in the same planeor on the same surface. The connection wiring fans-out away from thecontrol element 3104 and can connect to each of the functional elements3102 as shown in FIG. 31.

FIG. 32 is an example device 3200 including six 4×4 arrays of functionalelements each controlled by a single micro-assembled integrated circuit(e.g., as shown in FIG. 31). The array of control elements can beinterlaced within the array of functional elements using micro assembly.

FIG. 33 is an illustration of an example array 3300 using a controlelement 3302 to control different types of functional elements. Forexample, the array 3300 can include sixteen pixels 3306 a-3306 p(collectively 3306, although other numbers of pixels can be used). Eachpixel 3306 can include a red micro-LED 3304 a, a blue micro-LED 3304 b,and a green micro-LED 3304 c. The control element 3302 can process orread-out signals from sensing functional elements and also control orread-in signals to functional array elements. Thus, the array device canbe multi-functional and can perform many tasks on the same surface or inthe same plane or array area (e.g., hyper-spectral focal plane arrays).The array can use a single metal level and single control element forthe functional cluster.

FIG. 34 is an illustration of a display 3400 formed using microassembly. Each integrated circuit pixel cluster can act as anindependent display and each cluster of functional elements can beindependently operated from the control element. For example, smallportions of the overall device can be powered on when in use, and therest of the array device (a display for example) can remain powered off.FIG. 35 is an illustration of an example display 3500 in which a userhas selected to turn on just a portion of the overall device. FIG. 36 isan illustration of an example display 3600 in which a user has selectedto turn on just a portion of the overall device in a non-standard shape,for example a shape that is not rectangular.

FIG. 37 is an illustration of an example array 3700 with wireless dataor power input. The control element can be connected to integratedantennas 3702. Thus, display tiles can have data or power streamed intothe functional device array (e.g., display) using wirelesselectromagnetic transmission.

FIG. 38 is an illustration of a control element designed to havebuilt-in redundancy. For example, an extra control chip (as describedabove) can be printed per element cluster. Micro-assembled jumpers orcross-overs can be used to provide a means to electrically connect theback-up control element (e.g., connecting pad 3802 to pad 3804). Thus,as discussed above, a sparsely populated multi-functional array canprovide space for spare devices enabling additional functionality andcan use micro-assembled low-cost jumpers to connect to the sparedevices.

FIG. 39 is an illustration of an array 3900 with a control device 3904with built-in memory 3902. The control device 3904 can be an integratedcircuit control device that includes embedded memory. This enables arefresh-on-demand power-saving display for static images.

FIG. 40 is an illustration of a micro-assembled micro-LED display 4000with micro-assembled temperature-sensing elements 4002. Micro-assemblytechniques facilitate the formation of micro-assembled micro-LEDdisplays that include micro-assembled micro-LEDs 4004 a and 4004 b(collectively 4004) and micro-assembled IR or temperature-sensingdevices 4002. Displays that include temperature or IR sensing canprovide desirable data input capabilities, for example a touch-freehuman-device interface. IR or temperature-sensing devices, in someembodiments, include low band gap semiconductors (e.g., InGaAs,InGaAsSb, HgCdTe), pyroelectric materials (e.g., lithium tantalate orlithium niobate), thermopiles and other devices that respondelectrically to temperature gradients or temperature changes. In someembodiments, it is advantageous for the display to include one type oftemperature-sensing device. In some embodiments, the display includesmore than one type of temperature-sensing device.

In some embodiments, the micro-assembled display includes one or more ofseveral colors of micro-assembled micro-LEDs, several different types ofmicro-assembled IR or temperature-sensing devices, micro-assembledpassive electrical components, or micro-assembled control or memoryelements. In some embodiments, the number of sensing elements is lessthan the number of micro-LEDs in the display. In some embodiments, thenumber of sensing elements is equal to or larger than the number ofmicro-LEDs.

The disclosed technology, in some embodiments, provides a passive-matrixdisplay that uses inorganic micro-LEDs and a method of manufacturing thedisplay. Similarly, in some embodiments, the disclosed technologyprovides for active-matrix displays using inorganic micro-LEDs and amethod of manufacturing the display.

An image of a complete passive-matrix inorganic light-emitting diode(LED) display is shown in FIG. 41. This display includes a 360×90 arrayof micro-scale red LEDs. The micro-LEDs used in the display describedherein were prepared on their native substrate, partially removed fromthe substrate and the position of the micro-LEDs on the native substratewas maintained by a tether (e.g., a single, off-center tether for eachLED), and then micro transfer printed using a viscoelastic elastomerstamp. The micro-LEDs were formed on their native substrate with aresolution of approximately 3000 micro-LEDs per square inch. In someembodiments, the micro-LEDs are formed on their native substrate with aresolution of up to 10⁶ or 10⁸ micro-LEDs per square centimeter.

The illustrative display is designed to support a 128×128 pixel arrayusing red, green, and blue LEDs. Further, in this example, there are twosites for each color LED (red, green, and blue) in each pixel so that aredundancy scheme such as those described herein can be implemented (ifdesired). In this demonstration, red LEDs were populated into the greenand blue sub pixel sites. Other color micro-LEDs can be used in additionto red in order to produce a full-color display. The pixel size is 99×99microns as shown in FIG. 42, equating to 256 pixels per inch. Theemissive area is 11.88 mm×8.91 mm. The size of the glass substrate thatsupports the display is approximately 25 mm×25 mm.

FIG. 43 is an optical micrograph of a single pixel within the display.The micro-LEDs are connected to the metal rows and columns usingthin-film metal interconnects. The top-most metal (e.g., metal 2)connects to the lower metal (e.g., metal 1) through a via etched in adielectric layer deposited over metal 1. The micro-LEDs emit light inboth (all) directions, however, the metal contacts on the micro-LEDreflect the majority of the light down through the glass substrate.

FIG. 44 is an image of the completed display substrate (a glasssubstrate) with passive-matrix displays thereon. Sixteen displays areprinted to each 150 mm glass wafer. In some cases, fewer than 16displays are printed. FIG. 45 is an optical micrograph of the pixelarray of the display.

FIG. 46 is a flow chart illustrating a method 4600 for manufacturing apassive-matrix inorganic light-emitting diode display such as thedisplay shown in FIGS. 47A-B and 48A-B manufactured on a 150 mm glasswafer (0.7 mm thick). As discussed above, other substrates such assapphire and plastic can be used as the display substrate as well. Thedisplay substrate can be thin (e.g., 0.5 to 1 mm thick).

A first metal level was deposited and patterned on the wafer surfaceusing metal physical vapor deposition and photolithography techniques(4602). Specifically, negative-acting photoresist was exposed anddeveloped to create a lift-off template, the metal stack of Ti/Al/Ti wasdeposited using e-beam evaporation, and then the patterned metal layerwas completed by removing the lift-off template. Metal 1 includedAluminum (2000A) and Titanium (250A) stack. The purpose of the top-mostTitanium is to protect the Aluminum from passivating chemistries laterin the process flow.

A dielectric layer of silicon nitride is deposited onto the wafersurface (4604) to create an electrically insulating layer between Metal1 and Metal 2. Next, a thin polymer layer is spun onto the wafer surfaceusing a wafer spin-coater (4606). Here, a photosensitive negative-actingsemiconductor-grade epoxy from Dow Chemical Co. of Midland, Mich. (DowIntervia 8023) is used. The solvents are removed from the polymer usingheat treatments. Specifically, a soft bake on a hot plate at 140 degreesCelsius for 4 minutes, followed by a 30-min bake in an oven at 90degrees Celsius under flowing nitrogen.

Next, the micro-scale inorganic LEDs are micro-transfer-printed onto thesurface of the polymer (4608). The micro-transfer-printing was performedusing a print tool. The print process is facilitated using aviscoelastic elastomer stamp. The transfer process takes advantage ofthe kinetically tunable adhesion between solids (the LEDs) and theviscoelastic elastomer surface. To pick up the LEDs, the tool moves thestamp quickly away from the source surface, leading to an effectiveincrease in the adhesion between the elastomer and the chips. Duringprinting the print tool moves the stamp slowly away for the destinationsurface, thereby leaving the LED on the destination surface (e.g., thepolymer surface). In addition, the print step is aided by a lateralshear imparted to the stamp during the transfer process. The stamptransfers a 120×90 array of micro-LEDs to the display. To complete the360×90 display, three print operations are performed.

To make a full-color display (120 RGB×90), three separate printoperations are needed, one for the red, one for the green and one forthe blue light emitters. To achieve redundancy, additional LEDs can beprinted. In this example, six LEDs were printed to each pixel as shownin FIG. 43. Thus, this configuration can implement redundant micro-LEDs.

The pixel in FIG. 43 shows an example of six micro-LEDs within a single99×99 micron pixel. In this example, the full LED array was printed insix transfer operations. For the display shown here, only three subpixel sites are utilized (e.g., driven with the driver chip).

Following the transfer of the micro-LEDs, the polymer is first exposedto UV radiation and then cured in an oven at 175 degrees Celsius for 3hours under flowing nitrogen (4610). The UV exposure of the polymer isan important step to preventing the micro-LEDs from moving during theoven cure.

Next, a via (window) is formed through the dielectric layers (both thepolymer and silicon nitride) to expose the surface of Metal 1 (4612).This process is performed using standard photolithography (exposure anddevelopment of a positive-acting photoresist) and reactive ion etchingof the polymer and silicon nitride layers. The topmost Titanium on theAluminum serves to prevent the Aluminum from being passivated during thereactive ion etching step.

Next, a second metal (Metal 2) is deposited and patterned (4614). Thepurpose of Metal 2 is to contact both the anode and cathode of themicro-LED and to connect the anode to Metal 1 through the via. Thisprocess is achieved by first patterning a lift-off mask in anegative-acting photoresist, next depositing the metal stack(Ti/Al/Ti/Au), and finally lift-off of the photoresist mask to leavebehind the patterned metal wiring.

The wafer is sawn into individual displays using a dicing tool (4616)(e.g., a Dico dicing tool). The display wafer is coated with aprotective photoresist layer in advance of dicing, and this protectivephotoresist layer is solvent stripped from each individual display diefollowing dicing.

After cutting the individual displays from the wafer, a passive-matrixdriver IC is bonded to receiving pads on the surface of the glass wafer(4618). This is accomplished using standard “chip-on-glass” bondingprocedures, in which an anisotropic conductive film (ACF) is used tomake electrical connections between the metal (Metal 2) pads on theglass and the metal pads on the driver IC.

Next, a flexible printed circuit (cable) is attached to the display(4620) using “flex-on-glass” technology. Here an ACF film is used toelectrically interconnect the flexible printed circuit to the metal(Metal 2) pads on the display glass.

In this example, an FPGA driver board was used to send input (pictures)into the driver chip, and ultimately the display. The flexible printedcircuit connects the driver chip and display to the FPGA driver board.

FIGS. 47A-47B and 48A-48B are images of the working display. FIG. 47A isan image of the passive-matrix inorganic light-emitting diode displayand FIG. 47B is an enlarged image of the passive-matrix inorganiclight-emitting diode display. FIG. 48A is another image of thepassive-matrix inorganic light-emitting diode display and FIG. 48B is adifferent enlarged image of the passive-matrix inorganic light-emittingdiode display. FIG. 49A-49G are images demonstrating the displaytransparency. Ambient light is blocked by the metal lines and the smallLEDs, the remaining layers are transparent.

FIG. 50 is a micrograph of an example micro-LED display wired in apassive-matrix configuration. Micro-assembled LED displays use aplurality of micro-LEDs transferred from an epitaxial substrate to adisplay substrate (e.g., to a display substrate that is non-native tothe LEDs, such as plastic or glass) to produce a display. The discloseddisplay architecture establishes contact to both terminals of each LEDfrom the “top” of each LED. The conductive lines and spaces (or othershapes) that contact the anode of an LED are laterally separated fromthe conductive structures that contact to the cathode of the same LED.In this embodiment, the LED also has electrically contactable terminals(for example cathode and anode) laterally separated from each other.This configuration allows interconnection to the LEDs to be establishedusing panel processing or other large-area processing in which the linesand spaces are relatively coarse and inexpensive to form on a per areabasis (e.g., 2 micron lines and spaces to 2 mm lines and spaces). Forexample, the micro-LED display shown in FIG. 50 utilizes 2.5 μm and 5 μmconductive lines for the row lines 5004 a-5004 c, the column lines 5006a-5006 b, and interconnections 5008 a-5008 b.

In some embodiments, the electrically contactable terminals on themicro-LEDs are formed to occupy as much of the footprint of the LED areaas possible. Thus, in order to accomplish the lateral separation of thetwo terminals of the micro-LEDs, in some embodiments, the LEDs have alength significantly longer than its width. In some embodiments, theLEDs use fine lithography (for example wafer-scale lithography havingfeatures ranging from 100 nm to 20 microns) to reduce the separationdistance between the terminals.

For example, the LEDs 5002 a-5002 f as shown in FIG. 50 are rectangularmicro-LEDs. Specifically, in this example, the LEDs have a width of 3.5μm and a length of 10 μm. The elongated geometry is advantageous incertain embodiments, including when the terminals for each LED arelocated on one face of the LED. Among other things, the elongatedgeometry of the LED coupled with the large terminal electrodes providesfor ease of placement (e.g., decreasing the accuracy required to placeeach LED). In certain embodiments, the length-to-width ratio is greaterthan 2, for example, in a range from 2 to 5. In certain embodiments, theLEDs described herein have at least one of a width, length, and heightfrom 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm.

In some embodiments, the column electrodes (e.g., conductive lines 5006a-5006 b) are formed on a substrate. An insulating layer is applied overthe column electrodes. Holes 5010 a-5010 d are formed in the columnelectrodes to expose the column electrodes. The LEDs 5002 a-5002 f aremicro-transfer printed onto the insulating layer. Conductive materialcan be applied in a single level to form the row electrodes 5004 a-5004c and the interconnections (e.g., 5008 a-5008 b) to the columnelectrodes. The row electrodes 5004 a-5004 c electrically contact afirst terminal on the respective LEDs while the interconnections (e.g.,5008 a-5008 b) electrically connect a second terminal on a respectiveLED to a respective column electrode. Thus, the LED terminals (which areon the same face of the LED) can be connected on a single level. Forexample, the connection to the micro-LEDs can use a single photo maskand metal level (e.g., a single level) to establish connection to thetwo terminals of the LED.

FIG. 51 is an illustration of example printed LEDs wired in apassive-matrix configuration. The row electrode 5104 andinterconnections 5108 a-5108 b are formed on a single level. Theinterconnections 5108 a-5108 b are electrically connected to arespective column electrode 5106 a-5106 b. As shown in FIG. 51, theintersections between the interconnections 5108 a-5108 b and columnelectrodes 5106 a-5106 b, respectively, are uninsulated because holes5110 a and 5110 b are formed in the insulation as discussed above. Incontrast, the intersection between the row electrode 5104 and the columnelectrodes 5106 a-5106 b are insulated.

FIG. 52 is an optical micrograph of a single LED 5202 wired in apassive-matrix configuration (e.g., an enlarged image of a single LEDfrom FIG. 1). The LED 5202 includes a first terminal 5210 and a secondterminal 5212. Reducing the lateral separation between terminals 5210and 5212 of the LED and increasing the size of the terminals 5210 and5212 within the confines of the dimensions of the LED increases thetolerance for registration and lithography errors between the assembledmicro-LEDs and the relatively coarse conductive lines (5204, 5206, and5208) used to interconnect them on the display substrate.

FIGS. 53A-53B are illustrations of an example architecture of amicro-LED suitable for contacting both terminals from one face of theLED. FIG. 53A is a plan view of LED 5300 and FIG. 53B is a cross sectionof LED 5300. As shown in FIGS. 53A and 53B, terminals 5302 a and 302 bcover a substantial portion of the top of the LED 5300 and bothterminals 5302 a and 5302 b are on the top surface of the LED 5300. Thegap between the electrodes is minimized (e.g., a distance of 100 nm to100 microns) as discussed above. This configuration allowsinterconnection to the LEDs to be established using panel processing orother low-resolution large-area processing in which the lines and spacesare relatively coarse and inexpensive to form on a per area basis (e.g.,2 micron lines and spaces to 2 mm lines and spaces). In someembodiments, in order to accomplish the lateral separation of the twoterminals of the micro-LEDs 5300, the LED 5300 has a lengthsignificantly longer than its width. In some embodiments, the LEDs usefine lithography (for example wafer-scale lithography having featuresranging from 100 nm to 20 microns) to reduce the separation distancebetween the terminals.

The active layer is formed on a lateral conduction layer. The dielectricmaterial is deposited on the active material and one face of the activelayer and lateral conduction layer as shown in FIG. 53B. Terminal 5302 ais connected to the active layer and terminal 5302 b is connected to thelateral conduction layer.

In some embodiments, the LED emits a substantial majority of itsexternally emitted light downward. In these embodiments, theelectrically contactable/conductive terminals can be formed inreflective metals, including gold, silver, nickel, aluminum, and alloysthereof. In contrast, in the downward emitting embodiments, the lateralconduction structure is formed in a material that is transparent to thelight emitted from the LED, such as a semiconductor with a suitable bandgap or absorption edge selected to minimize absorption in the lateralconduction layer. Mirrors (not shown here) can be formed above the LEDsto further reflect light from the LED down.

In some embodiments, the LEDs are configured to emit a substantialmajority of its externally emitted light upward. In these embodiments,the electrically contactable/conductive terminals are formed intransparent materials, including transparent conductive oxides, ITO,ZnO, carbon nanotube films, and fine metal meshes. Also in the upwardemitting embodiments, the lateral conduction structure can be formed ina material that is transparent to the light emitted from the LED, forexample a semiconductor with a suitable band gap or absorption edgeselected to minimize absorption in the lateral conduction layer. Inthese embodiments the lateral conduction layer can also include anoptically reflective layer, including a dielectric mirror, a metalmirror and/or a material with high index of refraction to facilitatetotal internal reflection. Optically reflective materials or portions ofthe display substrate can be provided to reflect light from the LED up.

FIGS. 54A-54E illustrate embodiments of light-emitting diode structuresin accordance with embodiments of the present invention. As shown inFIG. 54A, the first electrical contact 5402 is on a first side of thesemiconductor element 5406 and the second electrical contact 5404 is onthe opposite side of the semiconductor element 5406. In this example,the first electrical contact 5402 is accessible from the top when thesemiconductor element 5406 is printed to the display substrate. Thefirst electrical contact 5402 is formed such that a portion of itextends beyond the edge of the semiconductor element 5406, therebyenabling access to the first electrical contact 5402 from the same sideof the structure as the second electrical contact 5404 when thestructure is printed to a display substrate 5410. This can beadvantageous when printed on a display substrate 5410 as both the firstand second electrical contacts 5402, 5404 are accessible for connectionin a common set of photolithographic steps.

FIG. 54B illustrates the light-emitting diode of FIG. 54A on the displaysubstrate 5410 with the first electrical contact 5402 in contact withthe first contact pad 5452 on the display substrate 5410. An electricalconnection 5450 can be made to the second electrical contact 5404 of theprinted semiconductor structure. The passivation layer 5419 preventsunwanted electrical conduction to the semiconductor element 5406 fromthe first and second wires 5450, 5452.

The structure illustrated in FIG. 54A can be formed by removing aportion of the semiconductor element 5406 (e.g., by etching) such that aportion of the first electrical contact 5402 is exposed (e.g.,accessible from the same side as the second electrical contact 5404)using photolithographic processes.

FIG. 54C illustrates an alternative structure locating both the firstand second electrical contacts 5402, 5404 on the same side of thesemiconductor element 5406. This structure is also made by removing aportion of the semiconductor element 5406, however, the removal ofsemiconductor material is stopped before the portion is etched entirelythrough the semiconductor element 5406 as done in the example shown inFIG. 54A, thereby leaving a cantilever extension 5408 of thesemiconductor element 5406. In one embodiment, the cantilever extension5408 is doped differently from the remainder of the semiconductorelement 5406. This, for example, allows the cantilever extension 5408 tobe more electrically conductive or to better prevent light emissionwhile the remainder of the semiconductor element 5406 is doped to emitlight in response to a current between the first and second electricalcontacts 5402, 5404.

FIG. 54D illustrates an alternative structure for a light-emittingdiode. This structure is similar to the structure shown in FIG. 54C,however, the first electrical contract 5402 is thicker such that thefirst electrical contact 5402 and second electrical contract 5404 have atop surfaces in the same plane or contacting a common surface. In someembodiments, this is advantageous as the light-emitting diode can beprinted to a display substrate with co-planar connection pads alreadyformed. This allows the light-emitting diode to electrically connect tothe display circuit upon printing it to the display substrate 5410.

After the cantilever extension 5408 is formed, the first electricalcontact 5402 is formed on the cantilever extension 5408 (e.g., byphotolithography). In some embodiments, both the first and secondelectrical contracts 5402, 5404 are formed at the same time or one afterthe other.

The structures described above in relations to FIGS. 54A, 54C, and 54Dcan be printed on a display substrate 5410 using a printing processemploying a stamp, such as an elastomeric stamp to form displays. FIG.54B illustrates the light-emitting diode of FIG. 54A on the displaysubstrate 5410 with the first electrical contact 5402 in contact withthe first contact pad 5452 on the display substrate 5410. An electricalconnection 5450 can be made to the second electrical contact 5404 of theprinted semiconductor structure. The passivation layer 5419 preventsunwanted electrical conduction to the semiconductor element 5406 fromthe first and second wires 5450, 5452. Similarly, FIG. 54E illustratesthe light-emitting diode of FIG. 54C on a display substrate 5406 withelectrical wires 5450, 5452 formed.

Having described certain embodiments, it will now become apparent to oneof skill in the art that other embodiments incorporating the concepts ofthe disclosure can be used. Therefore, the disclosure should not belimited to certain embodiments, but rather should be limited only by thespirit and scope of the following claims.

Throughout the description, where apparatus and systems are described ashaving, including, or comprising specific components, or where processesand methods are described as having, including, or comprising specificsteps, it is contemplated that, additionally, there are apparatus, andsystems of the disclosed technology that consist essentially of, orconsist of, the recited components, and that there are processes andmethods according to the disclosed technology that consist essentiallyof, or consist of, the recited processing steps.

It should be understood that the order of steps or order for performingcertain action is immaterial so long as the disclosed technology remainsoperable. Moreover, two or more steps or actions can be conductedsimultaneously.

What is claimed:
 1. An inorganic light-emitting diode comprising: aconduction layer having a top surface, a bottom surface, a firstconduction layer edge, and a second conduction layer edge; an inorganiclight-emitting layer disposed directly on and in contact with a portionof the top surface of the conduction layer, the inorganic light-emittinglayer having a first light-emitting layer edge and a secondlight-emitting layer edge, wherein the conduction layer comprises acantilever extension that extends beyond the second light-emitting layeredge to the second conduction layer edge; a first metal terminalcomprising a metal disposed directly on and in contact with a portion ofthe inorganic light-emitting layer and extending over and covering thefirst light-emitting layer edge and the first conduction layer edge; asecond metal terminal comprising the metal disposed directly on and incontact with a top surface of the cantilever extension of the conductionlayer and extending directly over and covering the second conductionlayer edge and covering at least a portion of the light-emitting layer,wherein the first metal terminal and the second metal terminal arereflective and a current supplied between the first metal terminal andthe second metal terminal causes the inorganic light-emitting layer toemit light such that the inorganic light-emitting diode emits a majorityof externally emitted light away from the first metal terminal and thesecond metal terminal; and a patterned dielectric layer disposeddirectly on and in contact with the inorganic light-emitting layer andthe conduction layer, wherein: the patterned dielectric layerelectrically isolates (i) the first metal terminal from the second metalterminal, (ii) the inorganic light-emitting layer from the second metalterminal and (iii) the first metal terminal from the conduction layer,the first metal terminal and the second metal terminal cover only aportion of the light-emitting layer and the conduction layer, the firstmetal terminal and the second metal terminal are separated by ahorizontal separation distance of from 1 μm to 10 μm, the first metalterminal and the second metal terminal together have a combined lengthgreater than the horizontal separation distance, the inorganiclight-emitting diode has a width from 1 μm to 10 μm, the inorganiclight-emitting diode has a length greater than twice the horizontalseparation distance, the length is greater than the width, the length ismeasured in a same direction as the horizontal distance, the width ismeasured in a direction perpendicular to and in a same plane as thelength, and the length is greater than the horizontal distance and spansthe first metal terminal and the second metal terminal.
 2. The inorganiclight-emitting diode of claim 1, wherein the inorganic light-emittingdiode has a height of from 0.5 to 10 μm.
 3. The inorganic light-emittingdiode of claim 1, wherein a surface of the first metal terminal and asurface of the second metal terminal share a plane.
 4. The inorganiclight-emitting diode of claim 1, wherein the conduction layer comprisesat least one member selected from the group consisting of asemiconductor substantially transparent to the light emitted from thelight-emitting diode, transparent conductive oxide, and thin metal mesh.5. The inorganic light-emitting diode of claim 1, wherein the firstmetal is a member selected from the group consisting of: aluminum,silver, gold, nickel, platinum, titanium, and alloys thereof.
 6. Aninorganic light-emitting diode display comprising a plurality ofinorganic light-emitting diodes according to claim 1, wherein theplurality of inorganic light-emitting diodes are disposed on a substratewith the conduction layer adjacent to the substrate, and the first metalterminal and the second metal terminal of each of the plurality ofinorganic light-emitting diodes are respectively electrically connectedto a respective first interconnection and a respective secondinterconnection disposed on the substrate.
 7. The inorganiclight-emitting diode display of claim 6, wherein the substrate is adisplay substrate having a thickness from 5 to 10 microns, 10 to 50microns, 50 to 100 microns, 100 to 200 microns, 200 to 500 microns, 500microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mm to 10 mm, or 10 mm to20 mm.
 8. The inorganic light-emitting diode display of claim 6, whereina resolution of the display is 120×90, 1440×1080, 1920×1080, 1280×720,3840×2160, 7680×4320, or 15360×8640.
 9. The inorganic light-emittingdiode display of claim 8, comprising a plurality of optical reflectionstructures, wherein an optical reflection structure of the plurality ofoptical refection structures is located on a same side of acorresponding light emitting diode of the plurality of light emittingdiodes as the first metal terminal.
 10. The inorganic light-emittingdiode display of claim 6, wherein the first interconnection and thesecond interconnection of each inorganic light-emitting diode of theplurality of light-emitting diodes are in a single metal layer.
 11. Theinorganic light-emitting diode display of claim 6, comprising aninsulator disposed over or under the first interconnection or secondinterconnection of each inorganic light-emitting diode of the pluralityof light-emitting diodes and wherein the first interconnection of eachinorganic light-emitting diode of the plurality of light-emitting diodesis electrically coupled to one column electrode of a plurality of columnelectrodes through a via of a plurality of vias in the insulator, eachvia associated with a light-emitting diode of the plurality oflight-emitting diodes.
 12. The inorganic light-emitting diode display ofclaim 6, wherein the first interconnection and the secondinterconnection of each inorganic light-emitting diode of the pluralityof light-emitting diodes have an interconnection width and are spacedapart by a distance greater than the interconnection width and adistance greater than the horizontal distance.
 13. The inorganiclight-emitting diode of claim 1, wherein the length of the inorganiclight-emitting diode is greater than or equal to two times its width.14. The inorganic light-emitting diode of claim 1, wherein the inorganiclight-emitting layer comprises a single material composition.
 15. Theinorganic light-emitting diode of claim 1, wherein the patterneddielectric layer electrically isolates the first metal terminal from thefirst light-emitting layer edge of the inorganic light-emitting layerover which the first metal terminal extends.